Spanish 2 Quiz: Combining Preterite And Imperfect
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Combining Preterite And ImperfectQuestion 1 of 15

A student translates the following English paragraph into Spanish: 'Every evening, Pedro walked along the river. One evening, while he was walking, he found an old letter in the grass. He picked it up and read it carefully.'

Which Spanish version most accurately captures the aspect contrasts of the original English passage — including the shift from habitual background to a specific interruption to completed sequential actions?

Todas las tardes, Pedro caminó por el río. Una tarde, mientras caminaba, encontraba una carta antigua en la hierba. La recogió y la leyó con cuidado.
Todas las tardes, Pedro caminaba por el río. Una tarde, mientras caminaba, encontró una carta antigua en la hierba. La recogió y la leyó con cuidado.
Todas las tardes, Pedro caminaba por el río. Una tarde, mientras caminó, encontró una carta antigua en la hierba. La recogía y la leía con cuidado.
Todas las tardes, Pedro caminaba por el río. Una tarde, mientras caminaba, encontró una carta antigua en la hierba. La recogía y la leía con cuidado.
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Spanish 2 Quiz

Spanish 2 Quiz: Combining Preterite And Imperfect

Practice Combining Preterite And Imperfect in Spanish 2 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 Combining Preterite And Imperfect, giving you a quick way to practice the rules, question types, and explanations that matter most for Spanish 2.

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 student translates the following English paragraph into Spanish: 'Every evening, Pedro walked along the river. One evening, while he was walking, he found an old letter in the grass. He picked it up and read it carefully.'

Which Spanish version most accurately captures the aspect contrasts of the original English passage — including the shift from habitual background to a specific interruption to completed sequential actions?

  1. Todas las tardes, Pedro caminó por el río. Una tarde, mientras caminaba, encontraba una carta antigua en la hierba. La recogió y la leyó con cuidado.
  2. Todas las tardes, Pedro caminaba por el río. Una tarde, mientras caminaba, encontró una carta antigua en la hierba. La recogió y la leyó con cuidado. (correct answer)
  3. Todas las tardes, Pedro caminaba por el río. Una tarde, mientras caminó, encontró una carta antigua en la hierba. La recogía y la leía con cuidado.
  4. Todas las tardes, Pedro caminaba por el río. Una tarde, mientras caminaba, encontró una carta antigua en la hierba. La recogía y la leía con cuidado.
Explanation: When translating between English and Spanish past tenses, your core task is mapping English verb phrases onto the preterite/imperfect distinction. Ask yourself for each verb: Is this habitual/ongoing background action (imperfect), or a completed, punctual event that moves the story forward (preterite)? The original passage has three distinct layers. First, "every evening, Pedro walked" signals habitual repetition — classic imperfect territory: caminaba. Second, "while he was walking" sets a continuous background for an interruption — again imperfect: caminaba. Third, "he found," "he picked it up," and "he read it" are all completed sequential actions that advance the narrative — all preterite: encontró, recogió, leyó. Answer B captures all three layers perfectly, making it the correct choice. Answer A fails immediately because caminó (preterite) in the first sentence treats the habitual evening walks as a single completed event rather than a repeated background habit — wrong aspect entirely. It also incorrectly uses encontraba (imperfect) for the moment of discovery, which should be a punctual, story-advancing event. Answer C gets the habitual opening right with caminaba, but then uses caminó inside the mientras clause — a contradiction, since mientras explicitly frames ongoing background action and demands the imperfect. It also uses recogía and leía (imperfect) for the sequential completed actions, leaving the story feeling unresolved. Answer D is the trickiest distractor: the first two clauses are correct, but it ends with recogía and leía (imperfect) instead of preterite, which blurs the completed sequential actions into vague, open-ended ones. A useful rule of thumb: mientras + imperfect frames the stage; preterite verbs are the actors who walk onto it.

Question 2

Ella se   (bañar) cuando se   (cortar) el dedo.

  1. bañó / cortó
  2. bañaba / cortaba
  3. bañó / cortaba
  4. bañaba / cortó (correct answer)
Explanation: The ongoing action of bathing sets the scene, so it uses the imperfect bañaba. The cutting is the sudden interruption, a completed one-time event, so it uses the preterite cortó. The tempting wrong choice uses bañó and cortó, but two preterites make both actions sound equally finished instead of showing the interruption.

Question 3

Yo   (caminar) por el parque cuando   (empezar) a llover.

  1. caminaba / empezó (correct answer)
  2. caminé / empezaba
  3. caminaba / empezaba
  4. caminé / empezó
Explanation: The first action 'walking' sets the scene, so it takes the imperfect 'caminaba'. The rain starting is a single completed event that interrupts, so it takes the preterite 'empezó'. The tempting trap is using two imperfects, which would make the rain's start a background action instead of the interruption.

Question 4

Yo   (ir) a salir cuando   (sonar) el teléfono.

  1. iba / sonó (correct answer)
  2. fui / sonaba
  3. iba / sonaba
  4. fui / sonó
Explanation: Being about to leave sets the background, so use the imperfect iba. The phone ringing is the single completed event that interrupts, so use the preterite sonó. The tempting error is iba / sonaba, which makes the ring ongoing instead of a finished interruption.

Question 5

  (ser) las tres cuando el tren   (llegar).

  1. Fueron / llegaba
  2. Eran / llegó (correct answer)
  3. Fueron / llegó
  4. Eran / llegaba
Explanation: Past time of day is background, so ser goes in the imperfect: eran las tres. The train's arrival is a completed one-time event, so llegar goes in the preterite: llegó. The tempting wrong answer uses llegaba, but imperfect would describe an ongoing or repeated arrival, not a single moment.

Question 6

Cuando yo   (tener) diez años,   (ganar) un concurso.

  1. tuve / ganaba
  2. tenía / ganaba
  3. tenía / gané (correct answer)
  4. tuve / gané
Explanation: When you were ten sets the background, so use imperfect tenía for age. Winning the contest is a completed one-time event, so use preterite gané. The tempting choice tenía / ganaba is wrong: ganaba would suggest you used to win it repeatedly or were in the middle of winning, not that you won once.

Question 7

Read the following mini-narration: 'Era una noche tranquila. Las estrellas brillaban y un viento suave soplaba entre los árboles. De repente, alguien llamó a la puerta.'

Which statement best analyzes the tense-aspect choices in this passage and explains why 'llamó' is in the preterite while the other verbs are in the imperfect?

  1. All four verbs could take the preterite with no meaningful change; the imperfects are a stylistic literary choice that adds atmosphere but does not alter the factual sequence of events
  2. 'Llamó' is preterite because it is the most recent action in the chronology; earlier verbs take the imperfect to indicate that they preceded the knock, following a rule of temporal distance from the present moment
  3. The three earlier verbs take the imperfect because they describe nature and setting, categories that always require the imperfect in Spanish; 'llamó' is preterite because human actions always take the preterite in past narration
  4. 'Era,' 'brillaban,' and 'soplaba' establish the continuous atmospheric background; 'llamó' is preterite because it is the single punctual, completed event that disrupts that ongoing scene, explicitly signaled by 'de repente' (correct answer)
Explanation: When analyzing past tense usage in Spanish narration, always ask yourself two questions: Is this verb describing an ongoing background condition, or is it a single, completed action that moves the story forward? In this passage, era, brillaban, and soplaba all paint the scene — the quiet night, the shining stars, the soft breeze. These conditions were already in progress, with no defined beginning or end. That is exactly what the imperfect is built for: continuous, habitual, or descriptive states in the past. Then llamó arrives. It is a single, instantaneous knock — one that interrupts everything. The phrase de repente ("suddenly") is your explicit signal that a punctual, boundary-defining event is occurring. That is the preterite's job: to record a completed action that either begins or ends a situation. Answer D captures this perfectly — the imperfects build an atmospheric backdrop, and the preterite punctures it. Answer A is wrong because the tense choices are not merely decorative. Switching the background verbs to preterite would chop the scene into disconnected snapshots, destroying the sense of an ongoing atmosphere being interrupted. Answer B confuses tense with simple chronological distance from the present, which is not how Spanish tense-aspect works — closeness to "now" is irrelevant here. Answer C invents false categorical rules. Setting and nature do not always require imperfect, and human actions do not always require preterite — context and aspect determine the choice every time. Your takeaway: watch for de repente, de pronto, or en ese momento in narratives — they almost always signal a preterite verb cutting through an imperfect background.

Question 8

Which of the following sentences contains a preterite/imperfect combination that is incorrect or unnatural for expressing a 'was doing…when…' interruption scenario?

  1. Dormíamos tranquilamente cuando el bebé se despertó y empezó a llorar — uses imperfect for the ongoing sleep and preterite for the sequence of sudden completed events
  2. Leía el periódico cuando sonó el timbre y tuve que abrir la puerta — uses imperfect for the ongoing reading and preterite for the interrupting doorbell and resulting action
  3. Estudiaba para el examen cuando mi compañero llegó y me interrumpía constantemente — uses imperfect for studying, preterite for the arrival, then imperfect again for the interrupting itself (correct answer)
  4. Miraba las noticias cuando apagué el televisor porque me aburría — uses imperfect for the ongoing watching, preterite for the decisive act of turning off, and imperfect for the ongoing boredom that motivated the action
Explanation: When Spanish describes a "was doing…when…" interruption, the formula is: imperfect for the background action + preterite for the interrupting event. The imperfect paints the scene; the preterite punctuates it. Problems arise when writers mix these aspects illogically after the interruption has already occurred. Option C is the problematic sentence. It starts correctly — estudiaba (imperfect) sets the ongoing study session, and llegó (preterite) captures the roommate's arrival as a completed, punctual event. But then it uses me interrumpía (imperfect) to describe the interrupting itself. Here's the issue: once the arrival happens and the interruption begins, if you want to say the roommate "kept interrupting" repeatedly, interrumpía could theoretically work for habitual/repeated action — but paired immediately after a preterite arrival in a single-event narrative, it creates an unnatural clash. The natural choice would be me interrumpió (preterite) to complete the chain of events, or restructuring entirely. Using imperfect for the interruption undermines the completed-action logic the sentence sets up. Options A, B, and D all demonstrate correct usage. In A, dormíamos (imperfect) + se despertó/empezó (preterite chain) is textbook interruption structure. In B, leía (imperfect) + sonó/tuve (preterite sequence) works perfectly — one interruption triggers a completed response. In D, miraba (imperfect) + apagué (preterite) + me aburría (imperfect for ongoing emotional state) is entirely natural and correct. Your strategy: after the interrupting preterite verb, ask yourself whether the next action is also completed/punctual — if yes, stay in preterite. Switching back to imperfect mid-chain signals habitual or background meaning, which often sounds jarring in single-event narratives.

Question 9

Elena recuerda aquella tarde perfectamente. Ella   (leer) su novela favorita en el jardín cuando de repente su teléfono   (sonar) con una llamada inesperada.

Which combination correctly fills in the two blanks in the passage, maintaining the proper preterite/imperfect contrast for a 'was doing…when…' narration?

  1. leía / sonó — the first verb describes the ongoing background action interrupted by the sudden completed event (correct answer)
  2. leyó / sonaba — the first verb marks the interrupting completed action and the second describes the continuous background state
  3. leía / sonaba — both verbs describe simultaneous ongoing background actions with no interruption indicated
  4. leyó / sonó — both verbs mark completed, sequential actions in a simple narrative chain without background context
Explanation: When you see a narration describing what someone was doing when something suddenly happened, you're being tested on the preterite/imperfect contrast — one of the most essential distinctions in Spanish-2. The classic framework is: imperfect sets the scene (ongoing, background action), while preterite marks the interruption (completed, sudden event). In this passage, Elena was reading her novel — a continuous, ongoing activity — when her phone rang unexpectedly. "Rang" is the interrupting event: it happened once, suddenly, and completely. "Was reading" is the background action that was already in progress. This means the first blank needs the imperfect (leía) and the second needs the preterite (sonó), making A the correct answer. It's the only choice that applies the right tense to the right role. B reverses the logic entirely — leyó (preterite) treats the reading as the interrupting completed event, and sonaba (imperfect) treats the phone ringing as ongoing background. That flips the meaning of the sentence upside down. C uses two imperfect verbs (leía / sonaba), which would imply both actions were simultaneous, ongoing background states — like saying "she used to read while the phone used to ring." There's no sense of interruption or a sudden event, which contradicts "de repente" (suddenly). D uses two preterite verbs (leyó / sonó), turning this into a simple sequence of completed actions: "she read, then the phone rang." This loses the background-scene-plus-interruption structure entirely. A useful memory aid: "was doing → imperfect; then BAM → preterite." The word de repente (suddenly) almost always signals a preterite interruption.

Question 10

A student writes: 'Cuando era niño, mi abuelo me contó historias todas las noches.' A classmate argues the sentence is incorrect and that 'contó' should be 'contaba.' Who is right, and why?

  1. The classmate is right because 'todas las noches' signals a habitual repeated action in the past, which requires the imperfect 'contaba' rather than the preterite 'contó' (correct answer)
  2. The student is right because 'cuando era niño' anchors the sentence in a specific completed past period, which triggers the preterite for all subsequent verbs in the same clause regardless of their frequency
  3. The classmate is right because any verb that follows 'cuando' in a past-tense clause must always take the imperfect in order to maintain grammatical tense agreement within the subordinate structure
  4. The student is right because the preterite 'contó' is the standard choice here — 'todas las noches' defines a bounded, finished period of time, and the preterite is always used to summarize actions within a closed time frame
Explanation: When choosing between the preterite and imperfect in Spanish, ask yourself one key question: does the action describe what happened (a completed event) or what was happening / used to happen (an ongoing or habitual condition)? This question tests exactly that distinction. The phrase "todas las noches" (every night) is your biggest clue. It signals a habitual, repeated action — something that kept happening over and over during childhood. In Spanish, habitual or repeated past actions belong to the imperfect tense. So "contaba" is the correct form, making A the right answer. The imperfect paints the background picture of what used to happen regularly, while "era niño" (also imperfect) reinforces that ongoing childhood context. B is wrong because "cuando era niño" establishes a general past timeframe, not a specific completed moment. It doesn't "trigger" the preterite for every verb that follows — tense choice still depends on the nature of each individual action. C is wrong because there is no rule requiring the imperfect after "cuando" as a blanket grammatical agreement rule. "Cuando" clauses can absolutely use the preterite (e.g., "Cuando llegué, comí"). D contains a tempting half-truth: yes, the preterite can summarize a finished period, but "todas las noches" emphasizes repetition, not a single summarized block. The preterite "contó" would imply he told stories exactly once. Your study tip: watch for frequency words like "siempre," "todos los días," and "cada semana" — they almost always signal the imperfect, regardless of what other time phrases surround them.

Question 11

Marcos   (caminar) por el centro histórico cuando   (ver) a su ex-novia. Ella   (llevar) un abrigo rojo y   (hablar) animadamente por teléfono. De repente, ella lo   (notar) y   (colgar) el teléfono.

Which sequence of verb forms correctly fills all six blanks in the passage above?

  1. caminaba / vio / llevaba / hablaba / notó / colgó — background actions use imperfect; the interrupting sightings and sudden reactions use preterite (correct answer)
  2. caminó / vio / llevaba / hablaba / notó / colgó — the first verb uses preterite because walking initiated the sequence; remaining verbs follow standard background/foreground rules
  3. caminaba / vio / llevó / habló / notó / colgó — all verbs describing Elena's state and actions take preterite since she is the secondary subject performing completed actions
  4. caminaba / veía / llevaba / hablaba / notaba / colgó — the verbs of perception and description all take imperfect, and only the final decisive action takes preterite
Explanation: When tackling a narrative passage in Spanish, your first job is to sort each verb into one of two categories: background description (what was ongoing, setting the scene) versus foreground action (what happened, changed, or interrupted). Background uses the imperfect; foreground uses the preterite. In this passage, Marcos was walking — an ongoing action that sets the scene — so caminaba (imperfect) is correct. Then he saw his ex-girlfriend: a specific, completed event that interrupts the background, so vio (preterite) is right. Her wearing the coat and talking on the phone are descriptive background details — they paint the picture of what was happening — so llevaba and hablaba (both imperfect) are correct. Finally, she noticed him and hung up the phone: two sudden, completed reactions that advance the story, so notó and colgó (preterite) are the right calls. That sequence matches A exactly. B is wrong because caminó (preterite) misreads Marcos's walking as a completed plot event rather than the ongoing backdrop in which the story unfolds. C incorrectly forces llevó and habló into preterite — the coat and the phone conversation aren't completed plot points; they're descriptive details, which demand imperfect regardless of who the subject is. D makes the opposite error with veía — the moment Marcos saw his ex is a specific, bounded event (a plot-changer), not an ongoing state, so imperfect is wrong there. A useful mental test: ask yourself, "Was this verb painting the background, or did it move the story forward?" If it moved the story, use preterite. If it described the scene, use imperfect.

Question 12

A Spanish instructor marks the following student sentence as partially incorrect: 'Yo conducía al trabajo cuando un perro cruzó la calle y yo frenaba bruscamente.' Which single correction would make the sentence grammatically and semantically accurate?

  1. Change 'cruzó' to 'cruzaba' — the dog's crossing serves as a background condition that was already in progress before the sudden braking, so it requires the imperfect
  2. Change 'conducía' to 'conduje' — driving to work is a completed action with a clear endpoint that occurred before the dog crossed, requiring the preterite for logical sequence
  3. Change 'frenaba' to 'frené' — the sudden braking is a completed, punctual reaction to the dog crossing, not an ongoing background state, so it requires the preterite (correct answer)
  4. Change 'conducía' to 'conduje' and 'cruzó' to 'cruzaba' — the main narrative events should both use preterite while descriptive elements use imperfect, requiring a swap of both subject verbs
Explanation: When you see a question about preterite vs. imperfect in Spanish, the core question to ask is: what role does each action play in the story? Background conditions and ongoing states use the imperfect (imperfecto), while completed, punctual events — especially sudden reactions — use the preterite (pretérito indefinido). In this sentence, the structure is almost correct. "Conducía" (imperfect) works perfectly: driving to work was an ongoing background action, the "scene" being set. "Cruzó" (preterite) is also correct: the dog crossing was a sudden, discrete event that interrupted the drive. The problem is "frenaba" — describing the braking with the imperfect implies it was an ongoing, habitual, or background state, which makes no semantic sense here. Slamming on the brakes is an immediate, completed reaction to the dog crossing. It happened once, suddenly, and finished. That demands the preterite: "frené." This makes C the correct fix. Answer A is wrong because the dog's crossing is not a background condition already in progress — it's the sudden interruption itself, which is precisely what the preterite captures. Changing "cruzó" to "cruzaba" would actually break the sentence's meaning. Answer B misidentifies "conducía" as the error; driving to work is the classic imperfect scenario — an ongoing action that gets interrupted — so it should stay imperfect. Answer D compounds the errors of B and A together, swapping both verbs incorrectly and inverting the logical grammar framework entirely. A useful rule of thumb: when you describe a sudden reaction to an event, especially with adverbs like bruscamente, the preterite is almost always required — reactions are punctual, not ongoing.

Question 13

Consider this sentence: 'Cuando llegué a casa, mi madre cocinaba.' A student claims this is equivalent in meaning to 'Cuando llegué a casa, mi madre cocinó.' Is the student correct?

  1. Yes — 'cocinaba' and 'cocinó' are interchangeable after 'cuando' because the conjunction itself specifies the temporal relationship, making verbal aspect redundant in this structure
  2. Yes — in both sentences 'llegué' is preterite, anchoring both in the same completed past moment, so the aspect of the second verb becomes interchangeable in everyday speech
  3. No — the first sentence is grammatically incorrect because two different aspect forms cannot coexist in the same 'cuando' clause; the second sentence is the only acceptable form
  4. No — the first sentence implies the cooking was already in progress when the speaker arrived; the second implies the mother started or finished cooking as a result of or at the same moment as the arrival (correct answer)
Explanation: When you see two past-tense verbs in a Spanish sentence, your first instinct should be to analyze aspect, not just tense. Spanish distinguishes between the preterite (a completed, bounded action) and the imperfect (an ongoing, background action) — and this distinction carries real meaning that cannot be ignored. In 'Cuando llegué a casa, mi madre cocinaba,' the imperfect cocinaba paints the cooking as an action already in progress when the speaker walked in — like a scene being described mid-action. The arrival interrupts or coincides with an ongoing activity. In 'Cuando llegué a casa, mi madre cocinó,' the preterite cocinó presents the cooking as a discrete, completed event — implying the mother started cooking, finished cooking, or did so in response to the arrival. These are genuinely different meanings, making D correct. A is wrong because conjunctions like cuando do not eliminate aspect — they simply establish a time frame. Aspect still communicates how the action relates to that moment. B is wrong because the preterite llegué anchors the arrival in time but says nothing about the nature of the second verb; the two verbs describe separate, independently aspectualized actions. C is wrong because it invents a grammar rule that doesn't exist — two different aspect forms absolutely can and regularly do coexist in a cuando clause. In fact, pairing a preterite with an imperfect (cuando llegué… cocinaba) is one of the most classic and correct structures in Spanish. As a study habit, whenever you see cuando + two past verbs, ask yourself: "Is one action the backdrop for the other?" If yes, the background action takes the imperfect.

Question 14

A student wants to say: 'I was about to leave when she called me.' She writes: 'Estaba a punto de salir cuando ella me llamaba.' What is the error, and what is the correct version?

  1. The error is 'estaba' — the phrase 'a punto de salir' implies an imminent completed action, which requires 'estuvo a punto de salir' (preterite) to show the near-departure was a finished event before the call
  2. The error is 'llamaba' — her calling is the sudden, bounded interruption, so it must be 'llamó' (preterite); 'estaba a punto de salir' correctly uses imperfect for the ongoing state of being on the verge of leaving (correct answer)
  3. The error is 'salir' — the infinitive should be replaced by 'saliendo' to form a progressive construction that more precisely mirrors the English 'was about to leave' in an ongoing sense
  4. There is no error — 'llamaba' is acceptable because when two past actions overlap in time, both verbs may take the imperfect, and the phone call overlapped with the state of being about to leave
Explanation: When translating a sentence like "I was about to leave when she called me," you need to think carefully about the Spanish preterite vs. imperfect distinction. The key question is: which action was an ongoing background state, and which was the sudden, completed interruption? The phrase estar a punto de + infinitive ("to be about to do something") describes a state — you were in the process of being on the verge of leaving. That's exactly what the imperfect is for: background conditions and ongoing states. So estaba a punto de salir is perfectly correct. The problem lies in llamaba. Her phone call is a specific, bounded event that interrupted the situation — it happened once, at a precise moment, and brought the scene to a turning point. That's the preterite's job. The correct sentence is Estaba a punto de salir cuando ella me llamó.* Answer B identifies this precisely. A is wrong because it misunderstands estar a punto de. The phrase itself doesn't describe a completed event — it describes an ongoing state (being on the verge), which the imperfect handles correctly. Switching to estuvo would actually distort the meaning. C is wrong because a punto de is a fixed prepositional construction that always takes an infinitive. Replacing salir with saliendo would be grammatically incorrect — Spanish doesn't use a gerund after prepositions in this structure the same way English does. D is wrong because two overlapping actions don't automatically both take the imperfect. The interrupting action — especially a sudden, one-time event — requires the preterite regardless of overlap. Study tip: When you see cuando linking two past actions, ask yourself which verb is the "background" and which is the "trigger event." Triggers almost always take the preterite.

Question 15

Which of the following sentences most accurately and naturally expresses the idea: 'She was sleeping when the earthquake struck'?

  1. Dormía cuando el terremoto golpeó — uses imperfect for the ongoing sleep and preterite for the sudden, bounded seismic event (correct answer)
  2. Durmió cuando el terremoto golpeaba — uses preterite for the sleep to mark its completion and imperfect for the earthquake to suggest it was an ongoing condition
  3. Dormía cuando el terremoto golpeaba — uses imperfect for both to show two simultaneous ongoing states, which fits a 'while…' construction rather than a sudden interruption
  4. Durmió cuando el terremoto golpeó — uses preterite for both to present the sleeping and the earthquake as two equally bounded, sequential events in a completed narrative
Explanation: When you see a sentence combining a background action with a sudden interruption, you're being tested on the preterite vs. imperfect distinction — one of Spanish's most important contrasts. Ask yourself: which action was ongoing in the background, and which action "broke in" as a completed, instantaneous event? In this sentence, the sleeping is the continuous background state — something already in progress. The earthquake striking, however, is a sudden, bounded event that interrupted that state. This classic interruption pattern calls for the imperfect (dormía) for the ongoing action and the preterite (golpeó) for the interruption. That's exactly what A provides, making it the most accurate and natural translation. B inverts the logic entirely — using the preterite for sleeping (as if it were a completed, bounded event) and the imperfect for the earthquake (as if it were a slow, ongoing condition). An earthquake "striking" is not an ongoing background state; this reversal is grammatically and semantically backwards. C uses the imperfect for both verbs (dormía... golpeaba), which would suggest two parallel, simultaneous ongoing states — more like "She was sleeping while the earthquake was rumbling." This works for a "while/mientras" construction but fails to capture the sudden, punctual nature of the seismic strike. D uses the preterite for both, presenting sleep and earthquake as two sequential, completed events in a narrative chain — more like "She slept; the earthquake struck." This loses the interrupted-background meaning entirely. Study tip: Memorize the interruption formula: imperfect = was doing (background) + preterite = sudden event (interruption). Whenever you see "when" (cuando) joining a background action to a sudden one, this pattern almost always applies.