Using the word "however" to join two independent clauses requires the use of a semicolon and a comma. In this case, "however" is not functioning as a conjunctive adverb. It is simply an adverb modifying the word "challenging." Because the modifier "however challenging" interrupts the independent clause, it is best to set it between commas.

Since there are eight schools in the Ivy League, the superlative comparison "best" is necessary in this sentence. "Best" would only be correct if Bale were being compared to one other school.

This sentence does not contain the correct punctuation where it is necessary. The sentence joins two related independent clauses together without the use of a coordinate conjunction; therefore, a semicolon is necessary between the words "investing" and "he." The correct choice is, "many books about investing; he wanted to become better."

This problem provides two very clear decision points for you to get started:

1. "they" vs. "it" as the first word of the sentence

2. "that of" vs. "those of" vs. (no possessive) in relation to "the Medieval period"

The key to both of these is recognizing the subject of the sentence which is "global temperatures." Since temperatures is plural, the pronoun that corresponds to them must be "they" and you can eliminate choices "it has only recently eclipsed the Medieval period, during which, scientists theorize, a" and "it has only recently eclipsed that of the Medieval period, during which scientists theorize a".

Then notice that the comparison is between current global temperatures and the temperatures during the Medieval period; you cannot logically compare "temperatures" with the timeframe, so you need to have "those of" (which "they have only recently eclipsed those of the Medieval period, during which scientists theorize that a" and "it has only recently eclipsed that of the Medieval period, during which scientists theorize a" have but "they have only recently eclipsed the Medieval period, during which scientists theorize that a" does not) to properly draw the comparison.

Between "they have only recently eclipsed those of the Medieval period, during which scientists theorize that a" and "they have only recently eclipsed those of the Medieval period, during which, scientists theorize, a", notice that the only difference is commas around "during which." Why is that important? Here you're dealing with a tense/timeline decision. Since "theorize" is present-tense but the Medieval period is clearly in the past (even if you're not a historian, the fixed past tense "sent" outside the underline tells you that those volcanoes were in the past), you cannot have "scientists theorize" as part of the phrase "during which." The scientists currently theorize that volcanoes caused the global warming, so you need to separate that subject-verb from the modifier "during (the Medieval period)." This means that answer choice "they have only recently eclipsed those of the Medieval period, during which, scientists theorize, a" is correct.

This sentence misuses a semicolon. Semicolons are used when joining two independent clauses without the use of a coordinate conjunction. Instead, in this sentence, a dependent clause is joined to an independent clause. The phrase "Even though Samretiredsinger and Apple are constantly engaged in legal battles" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct answer choice is, "Samretiredsinger and Apple are constantly engaged in legal battles, Samretiredsinger makes."

A semi-colon separates two independent clauses. No punctuation between "individualism" and "and" is necessary.

This sentence contains an error in verb voice. The phrase "Japanese longswords...are considered..." is in the passive voice. Since there is already an interrupting appositive renaming the subject here, it is best to simply re-phrase this sentence in the active voice in order to avoid an overly wordy and complex sentence. The most clear and concise choice in this instance is, "Many individuals consider Japanese longswords, katanas, the best swords in the world." The other choices are too wordy or contain inconsistencies (e.g. longswords...a katana).

This sentence contains no errors. All of the available choices are synonyms for "carry," but the difference lies in the point of reference. "Carry," "lift," and "truck" are generic words for carrying something, but "bring" indicates that you are carrying something to the position where the subject is, and "take" indicates you are moving away from the subject. The words "when coming to the music lesson" indicate that they are moving towards the direction of the subject: the music teacher (presumably, the teacher is already there). The correct choice is, "bring."

There are no errors in the above sentence. This sentence joins two related independent clauses without the use of a coordinate conjunction, so there should be a semicolon present after the word "time." In the other sentences, there are issues with parallelism (found...finds), verb agreement (loved to plays), word errors (freetime is not one word), or using a comma where a semicolon should be used. The correct choice is, "Christopher loved to play video games in his free time; he found playing them relaxing."

This sentence misuses a comma. This sentence is a simple sentence, so no punctuation of any sort is needed. The comma should be omitted because it comes in the middle of an independent clause. The correct choice is, "Many elements on the periodic table."