One can never say “If I would have done”. One can only say “If I had done”, which is called the past perfect verb form.

The word "thinking" is acting like a participle in the original sentence, making the first clause lack a verb. Changing "Many parents mistakenly thinking" to "Many parents mistakenly think" corrects the sentence's error.

The original statement uses the wrong verb tense for the verb "take"; it should be "took". The correct answer is also more concise than the original.

The original statement erroneously uses the past progressive verb tense "were believing" instead of "believed." The correct answer is also less awkward and more concise than the original.

The use of the verb "learn" is essentially as a modifier of the students "shock." This means that "learning" must be turned into a form that will describe why the students were "shocked." "Were shocked to learn," using an infinitive form, is the best choice among the answers.

The sentence features a conditional statement, "If she arrives empty handed," that explains the underlined portion of the sentence. This means the verb tense in the underlined portion should be in the future, as it will only occur once another action has taken place. "I will be angry," is the correct answer choice.

The use of the phrase "since the nineteenth century" indicates that the appropriate verb form of "sound" must be the past tense, as it describes things taking place previously. The correct answer choice is "has sounded throughout history," as it is the only choice in the past tense.

For this sentence, we need to correct the tense of the verb "go" such that it makes sense when used in the sentence with "stopped by." We know that Sam visited the grocery store "before he stopped by the bakery," so we need to pick out the past tense of "go," because we are told that Sam "stopped by" the bakery in the sentence, and "stopped by" employs the past tense. We also know that Sam visited the grocery store "before he stopped by the bakery," so the correct form of "go" must also employ the past tense. While both "went" and "gone" might look like potentially correct answers, "gone," when used as a verb, is the past participle of "go" and must be used with a helping verb like "has" or "had" to be grammatically correct. The answer choice "gone" does not include a helping verb, so we know that it can't be correct. "Went," however, is the past tense of "go," so "went" is the correct answer.

The sentence employs both the present-tense verb "make" and the past-tense verb "learned." Both of these verbs need to agree and employ the same tense. The only answer choice that correctly adjusts the tenses of the sentence's verbs is "Young professionals often make mistakes, but they also learn from them."

This sentence is structured as an independent clause about a priority and then a clarification of what that priority is.

The only appropriate punctuation here is a colon, which will provide that correct structural division and allow the second part of the sentence ("studying physics before her final exam the next morning") to act as an explanation of the noun "priority."

INCORRECT EXPLANATIONS:

A semicolon connects two separate independent clauses, so that is incorrect.

Janine's priority is "studying," which is a gerund, so the past tense "studied" is incorrect. 

The option that uses a comma is incorrect because the second clause is dependent and is lacking a subject.

The option that uses a colon unnecessarily includes the connector "and that was." These superfluous words cloud the sentence's meaning and make the sentence grammatically incorrect.