This sentence misuses the word "principal." The word "principal" is a title referring to the head of a school or organization or meaning a sum of money. The correct word here is "principle," which means a fundamental rule. No additional punctuation/changes are necessary. The difference between "would" and "will" is arbitrary in this sentence and does not change the meaning. The correct choice is, "students would learn the principles of marketing."

This sentence misuses the word "you're," which is a contraction meaning you are. The appropriate word here is "your" - the possessive form of "you." Everything else in the sentence is already correct. The other sentences either still misuse the word or misuse the punctuation in the sentence. The correct choice is, " "Even though it will not be collected, it is still important to do your homework." "

This sentence misuses the word "allusion." An "allusion" is an indirect reference to something and is often used to make references to literary works. It is clear from the context of the sentence that what is meant here is "illusion," a hallucination. The correct choice is, "Oscar suspected that he was beginning to see illusions."

This sentence misuses the word "it's." It's is a contraction for "it is," but it is clear from the context of the sentence that what is needed here is the possessive form of the word: its. The possessive form of "it" does not include an apostrophe before the s. Furthermore, the form " its' " is not an actual form of "it" - it is not a word - and no comma is necessary in this sentence. The best choice is, "with the introduction of its iPhone."

This sentence misuses the word "adverse." The word "adverse" means bad/detrimental. The word "averse" means opposed to/having a strong dislike of something. It is clear from the context of the sentence that the second definition is what is needed here. No additional changes are necessary. The correct choice is, "Sandra was averse to the idea."

This sentence uses the wrong word. The word "disinterested" means unbiased. The correct choice is "uninterested," which means not interested. The other choice all use common prefixes that mean "not" in English, but are not actually English words. The correct choice is, "The audience quickly became uninterested."

This sentence misuses the word "flout," which means to disregard/mock. Since the award belongs to the subject, it is unlikely that he would mock it. Instead, he is likely showing it off, which is the definition of the word "flaunt." The correct choice is, "He flaunted his award."

Note that a colon should not interrupt the main clause of this sentence.

This sentence misuses the word "proscribe," which means to forbid. The correct word here is "prescribe," which means to recommend. No punctuation is needed in this sentence because it is a simple sentence. The correct choice is, "The doctor prescribed some medicine for Misha's daughter."

This sentence misuses the word "shrunk." "Shrunk" is the participle form of the word "shrink," NOT the past tense form. You may say something like: "The shrunk shirt was no longer wearable" or "I have strunk the shirt," but NEVER "I strunk the shirt." The correct word here is "shrank." The correct choice is, "the amount of volunteers shrank." Note: the other choices cause issues in tense agreement/parallelism.

This sentence misuses the word "phenomena." The word "phenomena" is a plural noun. "The Wow! signal" is singular, so the correct word would be "phenomenon." Note: the use of the article "the" would not be appropriate because it would imply that the Wow! signal was the only thing that still confuses scientists, which is untrue. The correct choice is, "The Wow! signal was a phenomenon that still."