Conversational Mandarin Chinese Quiz: Supporting Opinions With Reasons
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Supporting Opinions With ReasonsQuestion 1 of 10

A test-taker is asked to give an opinion about living in a big city. They say: '大城市有很多机会，但是生活费用太高了，所以我更喜欢小城市。' (Big cities have many opportunities, but the cost of living is too high, so I prefer small cities.) Which of the following best describes the function of each connector in this response?

'但是' introduces the speaker's main reason for preferring small cities, and '所以' introduces the contrasting positive point about big cities — meaning the sentence reverses the typical roles of these two connectors for stylistic effect in spoken Mandarin.
'但是' and '所以' both function as conclusion connectors here: '但是' signals the first conclusion (that big cities have opportunities) and '所以' signals the second conclusion (that the speaker prefers small cities), forming a parallel two-part structure.
'但是' introduces a contrasting drawback that counters the positive aspect, and '所以' draws a conclusion from that drawback — together creating a supported opinion where the speaker's preference is explained through a chain of reasoning.
The two connectors function independently of each other: '但是' provides balance by acknowledging big cities, while '所以' simply restates the speaker's original preference for small cities without adding any new logical support to the argument.
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Conversational Mandarin Chinese Quiz

Conversational Mandarin Chinese Quiz: Supporting Opinions With Reasons

Practice Supporting Opinions With Reasons in Conversational Mandarin Chinese with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Supporting Opinions With Reasons, giving you a quick way to practice the rules, question types, and explanations that matter most for Conversational Mandarin Chinese.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A test-taker is asked to give an opinion about living in a big city. They say: '大城市有很多机会，但是生活费用太高了，所以我更喜欢小城市。' (Big cities have many opportunities, but the cost of living is too high, so I prefer small cities.) Which of the following best describes the function of each connector in this response?

  1. '但是' introduces the speaker's main reason for preferring small cities, and '所以' introduces the contrasting positive point about big cities — meaning the sentence reverses the typical roles of these two connectors for stylistic effect in spoken Mandarin.
  2. '但是' and '所以' both function as conclusion connectors here: '但是' signals the first conclusion (that big cities have opportunities) and '所以' signals the second conclusion (that the speaker prefers small cities), forming a parallel two-part structure.
  3. '但是' introduces a contrasting drawback that counters the positive aspect, and '所以' draws a conclusion from that drawback — together creating a supported opinion where the speaker's preference is explained through a chain of reasoning. (correct answer)
  4. The two connectors function independently of each other: '但是' provides balance by acknowledging big cities, while '所以' simply restates the speaker's original preference for small cities without adding any new logical support to the argument.
Explanation: When analyzing connector words (连词) in Mandarin, ask yourself: what logical relationship does each word create, and how do those relationships chain together to build the speaker's argument? In this sentence, '大城市有很多机会' establishes a positive premise. Then '但是' pivots to introduce a contrasting drawback: the cost of living is too high. This is the classic adversative function of '但是' — it signals "however, here's the counterpoint." Crucially, '所以' then picks up that drawback as its cause and delivers the speaker's preference for small cities as the logical consequence. The two connectors aren't working in isolation — they're linked in a chain: positive point → contrast → conclusion drawn from that contrast. This makes C the correct answer, as it captures both the contrast function of '但是' and the causal-conclusive function of '所以' working together to support the opinion. A is wrong because it inverts the actual roles of the connectors — '但是' does not introduce the main reason for preferring small cities, and '所以' does not introduce the positive point. That reversal simply doesn't reflect what the sentence says. B is wrong because it misidentifies '但是' as a conclusion connector. '但是' signals contrast, not conclusion — '所以' is the only conclusion marker here. D is wrong because it claims '所以' merely restates the preference without adding logical support. In reality, '所以' explicitly derives the preference from the high cost of living, which is logical support by definition. A useful tip: in Mandarin opinion responses, watch for the pattern 优点 + 但是 + 缺点 + 所以 + 结论 — this is a very common and natural argumentation structure you should both recognize and produce.

Question 2

Listen to the following conversation: Ming: 你为什么不喜欢那家餐厅？(Why don't you like that restaurant?) Li: 因为那家餐厅的服务很慢，所以我不想去。(Because the service at that restaurant is very slow, so I don't want to go.)

Li uses two connectors in her response. Which of the following best describes how she structures her opinion?

  1. She states her opinion first, then gives a reason using '因为,' and adds a conclusion using '所以' — forming a complete cause-and-effect chain that supports her position. (correct answer)
  2. She introduces a contrasting view using '但是' and then states her personal preference, using '所以' to introduce the reason why she disagrees with the opposing view.
  3. She uses '因为' to introduce her conclusion and '所以' to introduce the background information, reversing the typical cause-and-effect order so that the stronger point comes first.
  4. She gives her reason using '因为' and then uses '所以' to restate the original question, forming a rhetorical structure that echoes the prompt rather than providing a supported opinion.
Explanation: When you see a question asking how a speaker "structures" their response using connectors, your job is to map the logical flow — identify what each connector does and whether the overall pattern matches the description given. In Li's sentence, 因为...所以... (yīnwèi...suǒyǐ...) forms a classic cause-and-effect pair: 因为 introduces the reason (the service is slow), and 所以 introduces the result or conclusion (she doesn't want to go). This is exactly what A describes — a complete, well-structured cause-and-effect chain that directly answers Ming's question and supports Li's position. A is correct. B is wrong because it introduces 但是 (but/however), a contrast connector that never appears in Li's sentence. Li isn't countering an opposing view — she's directly explaining her own preference. C gets the roles of 因为 and 所以 backwards. In standard Mandarin grammar, 因为 always introduces the cause, and 所以 always introduces the effect. Li's sentence follows this conventional order perfectly — C describes the opposite, which is both grammatically unusual and inaccurate here. D is wrong because 所以 in Li's sentence introduces a new conclusion (not wanting to go), not a repetition of Ming's question. Li provides a genuine, supported opinion — there's nothing rhetorical or circular about her structure. A useful tip: whenever you see 因为...所以... in a sentence, mentally label the clauses as CAUSE → EFFECT. That pairing is one of the most common logical structures in conversational Mandarin, and exam questions will often test whether you can correctly identify which clause carries the reason versus the conclusion.

Question 3

A Mandarin speaker says: '这本书很有意思，所以我推荐你读。' (This book is very interesting, so I recommend you read it.) Which of the following is the most accurate analysis of how this sentence supports an opinion?

  1. The sentence uses '所以' to link an observation (the book is interesting) to a recommendation, implying a cause-and-effect relationship where the book's quality is the unstated reason and the recommendation is the conclusion. (correct answer)
  2. The sentence is missing a required '因为' before '这本书很有意思'; without it, '所以' cannot function as a conclusion connector, and the sentence fails to properly support the opinion according to standard Mandarin grammar rules.
  3. The sentence uses '所以' as a contrast connector in this context, meaning the speaker is recommending the book despite finding it only somewhat interesting — an advanced rhetorical use of the connector in spoken Mandarin.
  4. The sentence is a fully supported opinion, but '所以' here introduces the reason (the book is interesting) rather than the conclusion (the recommendation), reversing its typical role for emphasis in informal speech.
Explanation: When analyzing how Mandarin sentences express opinions, focus on logical connectors — specifically how words like '所以' (suǒyǐ, "therefore/so") and '因为' (yīnwèi, "because") structure cause-and-effect reasoning. In this sentence, '这本书很有意思' (the book is very interesting) serves as the observation or premise, and '所以我推荐你读' (so I recommend you read it) is the conclusion drawn from that premise. This is exactly how '所以' works: it signals that what follows is the result or recommendation justified by what came before. Answer A captures this perfectly — the book's quality is the implicit cause, and the recommendation is the logical conclusion. The sentence functions as a complete, coherent opinion even without an explicit '因为.' Answer B is a common misconception. While '因为...所以...' is a classic paired structure in Mandarin, '所以' does not require '因为' to appear before it. Using '所以' alone to introduce a conclusion is grammatically correct and extremely common in both spoken and written Mandarin. Don't be tricked into thinking the paired structure is mandatory. Answer C misidentifies '所以' as a contrast connector — that role belongs to words like '但是' (but) or '虽然...但是...' (although...but). There is no sense of contrast or concession in this sentence. Answer D reverses the actual function of '所以.' In this sentence, '所以' introduces the conclusion (the recommendation), not the reason. That misreading directly contradicts how the connector works. Your study tip: remember that '因为' introduces reasons, '所以' introduces conclusions — and either can appear alone without its paired partner in natural Mandarin speech.

Question 4

An examiner asks a test-taker: '你觉得学中文难吗？' (Do you think learning Chinese is difficult?) The test-taker responds: '我觉得中文有点难，但是很有意思。' (I think Chinese is a bit difficult, but it's very interesting.)

The examiner marks this response as demonstrating connector use but NOT fully demonstrating the skill of 'supporting an opinion with a reason.' What is the most likely reason for this evaluation?

  1. The response would be stronger if '因为' introduced the difficulty as a reason and '所以' concluded that the test-taker still enjoys Chinese — replacing '但是' with this structure would make the opinion more explicitly supported with cause-and-effect logic.
  2. The response is marked down because '但是' is not one of the accepted connectors for opinion support on this exam; only '因为' and '所以' are recognized as valid reason-supporting connectors, so the use of '但是' does not count toward the skill.
  3. The response fails because using the opinion word '觉得' (think/feel) before a connector is non-standard; exam guidelines require connectors to appear only in sentences that begin directly with a statement of fact rather than a subjective marker.
  4. The response uses '但是' to contrast two observations about Chinese, but never provides a reason that directly supports the test-taker's overall opinion — there is no '因为' or '所以' linking a cause to a conclusion about whether Chinese is worth learning. (correct answer)
Explanation: When evaluating spoken Chinese responses, examiners distinguish between two related but separate skills: using connectors and supporting an opinion with a reason. A connector simply links two clauses; supporting an opinion requires explaining why the speaker holds that view — typically using cause-and-effect logic with words like '因为' (because) or '所以' (therefore). In this response, '我觉得中文有点难，但是很有意思' uses '但是' to contrast two observations — difficulty versus interest. That earns credit for connector use. However, the test-taker never explains why Chinese is difficult or why it's interesting, and never draws a conclusion from those reasons. The opinion ('I think Chinese is a bit difficult but interesting') floats without any logical support underneath it. That's exactly why D is correct — '但是' creates contrast, not causation, and no '因为/所以' structure links a reason to the overall opinion. A is tempting but goes too far. It describes a stronger version of the response rather than diagnosing what's actually missing — and it implies replacing '但是' entirely, which isn't the key issue. B is simply false; '但是' is a legitimate and recognized connector on this exam. The problem isn't which connector was used — it's what that connector accomplishes. C invents a rule that doesn't exist. Using '觉得' before a connector is completely standard in conversational Mandarin and raises no issue here. Your study tip: always ask yourself, "Did I give a reason, or just a reaction?" If your response only describes how you feel without a '因为' explaining why, you've expressed an opinion but haven't supported it.

Question 5

Read the following two responses to the question '你为什么喜欢运动？' (Why do you like exercise?): Response A: '因为运动对身体好，所以我喜欢运动。' (Because exercise is good for the body, so I like exercise.) Response B: '我喜欢运动，因为运动对身体好。' (I like exercise because exercise is good for the body.)

A teacher tells students that both responses are correct examples of supporting an opinion with a reason, but they follow different structural patterns. Which statement BEST explains the key structural difference between the two responses?

  1. Response A uses '因为' as a subordinating connector and '所以' as a coordinating connector across two independent clauses, while Response B uses '因为' as both a subordinating and a coordinating connector within a single clause.
  2. Response A is more formal and complete because it uses both '因为' and '所以,' while Response B is incomplete because omitting '所以' means the conclusion is not explicitly stated, making it a weaker example of opinion support.
  3. Response B is more natural and correct in spoken Mandarin because native speakers always state their opinion before their reason, whereas Response A's structure is only used in formal written Chinese, not in conversation.
  4. Response A places the reason before the opinion using the '因为...所以' paired structure, while Response B places the opinion first and attaches the reason afterward using '因为' alone — both are valid but reflect different Chinese sentence-order options. (correct answer)
Explanation: When you see a question about Mandarin sentence structure involving reasons and opinions, focus on where the connectors appear and what order the ideas follow — not on formality or completeness alone. In Mandarin, the paired structure 因为...所以... works like a "because...therefore..." frame: the reason comes first, then the conclusion follows. Response A does exactly this — it leads with the reason clause ("因为运动对身体好") and lands on the opinion ("所以我喜欢运动"). Response B flips the order, stating the opinion first ("我喜欢运动") and then attaching the reason with "因为" alone. Both are grammatically correct and naturally used in spoken Mandarin — they simply reflect two different valid word-order options. That's precisely what D describes, making it the correct answer. Answer A is wrong because it mischaracterizes the grammar. "因为" and "所以" are both subordinating/coordinating conjunctions that work together as a paired set — describing one as "subordinating" and the other as "coordinating" across "independent clauses" is linguistically inaccurate and confuses the structure. Answer B is wrong because omitting "所以" does not make a sentence incomplete or weaker. "因为" used alone after a stated opinion is a perfectly standard, complete construction in Mandarin — the conclusion is already explicit in the first clause. Answer C is wrong because it overstates a rule that doesn't exist. Neither structure is restricted to formal writing or spoken conversation — both appear freely in everyday Mandarin speech. As a study tip: don't assume that more connectors means more correct in Mandarin. Focus on recognizing that word order flexibility is a feature of the language, not a sign of error.

Question 6

A language learner produces the following sentence: '我不去那个派对，因为我很累，但是我会给你打电话。' (I'm not going to that party because I'm tired, but I will call you.)

An evaluator praises this sentence as a strong example of supporting an opinion with reasons using multiple connectors. A second evaluator disagrees, saying the connectors are not all functioning as reason-support. Which position is more accurate, and why?

  1. The second evaluator is more accurate, but for a different reason: '因为' is used incorrectly here because it follows the opinion rather than preceding it, which means only '但是' is functioning as a proper connector in this sentence.
  2. The first evaluator is more accurate: both '因为' and '但是' function as reason connectors in this sentence because they each introduce information that explains the speaker's decision not to attend the party.
  3. The second evaluator is more accurate: '因为' correctly supports the opinion (not going) with a reason (tired), but '但是' introduces a separate compensating action (calling), which is a contrast, not a reason that supports the original opinion about the party. (correct answer)
  4. The first evaluator is more accurate: in spoken Mandarin, '但是' always functions as a reason connector when it follows a '因为' clause, making both connectors part of a unified reason-support structure in this sentence.
Explanation: When analyzing sentences with multiple connectors, your job is to examine what function each connector performs — not just count them. Ask yourself: does this word introduce a reason, a contrast, a condition, or something else entirely? In this sentence, '因为' (because) introduces the reason "I'm tired" to explain why the speaker isn't going to the party. That's textbook reason-support: opinion → connector → justification. '但是' (but/however), on the other hand, introduces a contrasting action — calling the person — which doesn't justify the decision to skip the party. It pivots to a concession or compensation. These are two distinct rhetorical moves. So the second evaluator is right, and C is the correct answer: '因为' supports the opinion with a reason, while '但是' signals contrast, not support. A is wrong because it misidentifies the problem with '因为.' In Mandarin, '因为' can legitimately follow the main clause — both "我不去，因为我累" and "因为我累，我不去" are grammatically acceptable. The word order isn't the issue here. B is wrong because it incorrectly claims '但是' functions as a reason connector. '但是' signals contrast or shift in direction — it never introduces a supporting reason in standard Mandarin usage. D is wrong because it invents a rule that doesn't exist. '但是' does not transform into a reason connector simply because it follows a '因为' clause. Each connector retains its own independent function regardless of what precedes it. When studying connectors in Mandarin, always map each one to its specific function: reason (因为), contrast (但是), condition (如果), concession (虽然). Mixing up their roles is one of the most common errors in connector-based questions.

Question 7

A teacher gives students three sentence frames and asks them to identify which one correctly supports an opinion with a reason: Frame 1: '[Opinion], 所以 [Reason]' Frame 2: '因为 [Reason], 所以 [Opinion]' Frame 3: '[Opinion], 因为 [Reason]'

Which of the following statements about the three frames is CORRECT?

  1. All three frames are correct ways to support an opinion with a reason, but Frame 1 is the most common in spoken Mandarin because native speakers often state their conclusion before explaining their reasoning.
  2. Only Frame 2 and Frame 3 correctly place the reason in a logical position relative to the opinion; Frame 1 inverts the cause-and-effect relationship by putting '所以' before the reason rather than before the conclusion. (correct answer)
  3. Only Frame 2 is correct because it is the only frame that uses both '因为' and '所以' together, and exam guidelines require both connectors to be present for a response to be considered a fully supported opinion.
  4. Frame 3 is incorrect because placing '因为' after the opinion is a grammatical error in Mandarin; '因为' must always appear at the beginning of a sentence or clause to function as a reason connector.
Explanation: When you see a question about connecting reasons to opinions in Mandarin, focus on what each connector actually signals: 因为 (yīnwèi) introduces a cause or reason, while 所以 (suǒyǐ) introduces a result or conclusion. Logical structure requires the cause to precede 所以, and the opinion (conclusion) to follow it. Frame 2 ("因为 [Reason], 所以 [Opinion]") is the gold standard — it explicitly marks both the reason and the conclusion, flowing naturally from cause to effect. Frame 3 ("[Opinion], 因为 [Reason]") is also valid: you state your opinion first, then justify it with 因为. This mirrors natural speech where someone makes a claim and follows it with supporting reasoning. Both frames correctly position the reason in a logical relationship to the opinion, making B the correct answer. A is tempting because it sounds culturally reasonable, but it's wrong — Frame 1 ("[Opinion], 所以 [Reason]") is the problem child. Using 所以 before what is supposed to be the reason (not the conclusion) reverses the cause-effect logic entirely. 所以 signals "therefore," so whatever follows it must be the result, not the cause. Frame 1 is genuinely incorrect, not just stylistically informal. C is wrong because grammatical correctness doesn't require both 因为 and 所以 to appear together. Using one connector alone is perfectly acceptable in Mandarin. This is a fabricated rule. D is wrong because placing 因为 mid-sentence (after the opinion) is grammatically standard, not an error — it's exactly how Frame 3 works. Remember: 所以 always points forward to a conclusion, never backward to a reason. If you keep that arrow in mind, you can quickly spot inverted logic in any frame.

Question 8

Two friends are discussing whether to take an online class or an in-person class. Friend A says: '我觉得网课比较方便，因为不用去学校。' (I think online classes are more convenient because you don't have to go to school.) Friend B replies: '网课方便，但是上课的时候容易分心，所以我更喜欢面授课。' (Online classes are convenient, but it's easy to get distracted, so I prefer in-person classes.)

Which of the following best explains why Friend B's response is considered a MORE complete demonstration of the target skill than Friend A's response?

  1. Friend B's response uses more connectors, which automatically makes it a stronger demonstration of the skill because exam rubrics assign credit based on the total number of connectors used, rewarding quantity of connector use over logical structure.
  2. Friend B acknowledges a positive point, then uses '但是' to introduce a contrasting drawback, and finally uses '所以' to draw a conclusion — creating a three-step supported opinion. Friend A only connects one reason to one opinion without addressing a counterpoint or stating a final conclusion. (correct answer)
  3. The two responses are actually equally complete because each one uses exactly one reason-support connector — '因为' for Friend A and '所以' for Friend B — making them equivalent in terms of how well they demonstrate the target skill.
  4. Friend B's response is stronger because '但是' and '所以' are classified as higher-level connectors than '因为' on standard Mandarin proficiency scales, and using higher-level connectors always produces a more complete demonstration of opinion support.
Explanation: When evaluating how well someone expresses and supports an opinion in conversational Mandarin, you're not just counting connectors — you're looking at the logical architecture of what they say. A complete, well-supported opinion typically moves through three steps: state a position, acknowledge complexity or contrast, and draw a conclusion. Friend B does exactly this. By first conceding that online classes are convenient, then using 但是 to introduce the drawback of distraction, and finally using 所以 to arrive at a personal conclusion, Friend B builds a three-part argument. Friend A, by contrast, states one opinion and gives one supporting reason with 因为 — that's a valid sentence, but it's a single-step structure with no counterpoint and no conclusion. This is why B is the correct answer: it precisely identifies this structural difference and explains why that difference matters. A is wrong because rubrics don't reward raw connector count. A sentence stuffed with connectors but no logical flow would not score well — quality of reasoning matters, not quantity of linking words. C is wrong because it treats 因为 and 所以 as equivalent single-step connectors, ignoring that Friend B's response actually uses two connectors to build a multi-step argument, not just one. D is wrong because no standard proficiency scale ranks 但是 and 所以 as inherently "higher-level" than 因为. The strength comes from how connectors are used together, not from a tier system. When you practice opinion expressions in Mandarin, train yourself to think in three beats: concede → contrast → conclude. That pattern signals conversational maturity and is exactly what examiners look for.

Question 9

Four students each give an opinion about their favorite season. Read their responses: Student 1: '我喜欢春天，因为天气很好。' (I like spring because the weather is nice.) Student 2: '夏天太热了，所以我不喜欢夏天。' (Summer is too hot, so I don't like summer.) Student 3: '秋天很漂亮，但是冬天也不错。' (Autumn is beautiful, but winter is also not bad.) Student 4: '我不喜欢冬天，因为太冷了，所以我更喜欢夏天。' (I don't like winter because it's too cold, so I prefer summer.)

Which student's response BEST demonstrates the skill of supporting an opinion with a reason using connectors, and why?

  1. Student 4, because they use both '因为' and '所以' to build a full chain — a stated opinion, a reason, and a conclusion — making the supported position the clearest and most complete of the four responses. (correct answer)
  2. Student 1, because using '因为' to directly follow an opinion with a reason is the most straightforward demonstration of opinion support with a connector, and the two-part structure is sufficient on its own.
  3. Student 3, because using '但是' shows the ability to hold two viewpoints simultaneously, which reflects a more sophisticated level of reasoning than simply attaching a single reason to an opinion.
  4. Student 2, because placing the reason before the opinion and using '所以' to draw the conclusion reflects the most natural and complete Chinese sentence structure for expressing a supported view.
Explanation: When evaluating how well a student supports an opinion with reasons, you're looking for more than just presence of a connector — you're assessing the completeness of the logical chain: is there an opinion, a reason, and a conclusion all working together? Student 4's response does exactly this. They open with a stated opinion ("我不喜欢冬天"), immediately support it with a cause using 因为 ("太冷了"), and then draw a contrasting conclusion using 所以 ("我更喜欢夏天"). Together, 因为 and 所以 form a complete cause-and-effect framework — because X, therefore Y — anchored to a clear position. This makes A the correct answer. Here's why the other choices fall short. B overstates Student 1's response. While 因为 correctly links an opinion to a reason, the structure is minimal — there's no conclusion or elaboration, so the "support" is thin. C misidentifies what the question is actually testing. Student 3 uses 但是 (but/however), which contrasts two opinions rather than supporting one with a reason — sophistication in structure doesn't equal skill in opinion support with connectors. D is factually misleading. Student 2 uses 所以, but the sentence leads with a complaint rather than a stated opinion, and 所以 is used to restate the same feeling — it's circular, not a full supported argument. A good study habit here: when you see 因为...所以... used together in the same sentence, recognize it as a complete logical unit — reason + conclusion. That paired structure is one of the clearest signals of a well-supported opinion in Mandarin.

Question 10

A student is asked to express an opinion about studying abroad. She says: '我想去国外学习，但是费用太高了。' (I want to study abroad, but the cost is too high.)

The student's response uses '但是' (but) to connect two ideas. A language evaluator notes that her opinion is only partially supported. Why is her response considered incomplete as a supported opinion?

  1. She introduces a contrasting idea with '但是' but never resolves the contrast with a conclusion connector like '所以,' leaving her final position on studying abroad unclear to the listener. (correct answer)
  2. She uses '但是' correctly, but the statement is too short to count as a supported opinion because exam standards require at least three sentences with connectors.
  3. She should have used '因为' instead of '但是' because opinions in Mandarin must always be supported with a reason introduced by a cause connector, not a contrast connector.
  4. Her opinion is complete because '但是' functions as a reason connector in this context, and the high cost directly explains why she is hesitant about studying abroad.
Explanation: When evaluating whether an opinion is fully supported in Mandarin conversation, you need to think about logical completeness — does the speaker actually land somewhere? Connectors like '但是' signal contrast, while connectors like '所以' signal conclusion. A well-formed opinion typically moves through contrast toward a resolved stance. In this student's response, she opens with a desire ('我想去国外学习') and introduces a complication ('但是费用太高了'). That contrast creates tension — but she never resolves it. The listener is left wondering: so does she plan to go? Save money? Give up? Without a conclusion connector like '所以' to deliver her final position, the opinion floats unresolved. That's exactly what A identifies — the contrast is introduced but never closed with a conclusion, leaving her stance ambiguous. B is a trap that invents a rule. No standard exam framework requires a minimum sentence count with connectors. Complete opinions are judged by logical structure, not sentence quantity. C misunderstands the role of '因为.' Cause connectors and contrast connectors serve different purposes — neither is universally required for opinions. Using '但是' is perfectly appropriate here; the problem is what comes after it. D is the most dangerous distractor because it sounds reasonable — yes, the high cost does explain her hesitation — but '但是' is a contrast connector, not a reason connector, and the statement still lacks a resolved conclusion. As a study tip: whenever you see '但是' in a structured opinion, ask yourself — where is the '所以'? A complete opinion arc in Mandarin typically follows: position → contrast → conclusion.