This sentence misuses the word "who's," which is a contraction for "who is." The context of the sentence tells us that the pronoun should be possessive. The correct form is "whose."

This sentence misuses the word "that." The word "that" does not begin a new clause; therefore, there should not be a comma before the word. Either "that" needs to be changed to "which," or the comma needs to be omitted. The choice that corrects this issue is, "areas, which ultimately led to her new invention."

This sentence uses the wrong pronoun. The word "which" is never used for nouns which refer to humans. The correct choice here is "who." No other changes are necessary. Note that "that" does not begin a relative clause (in which case you would have to omit the commas), and the word "being" generally has to do with existence and is never used in this way. The correct choice is, "the teens, who were excited, bought much food."

This sentence misuses the word "which." Since the sentence is about the Presidents (this is the subject), "which" is inappropriate as it can only refer to non-humans (Additionally, nations cannot "convene," but representatives (i.e. people) from those nations can). If the relative clause were to be re-written, it would be "they convened to talk about world issues." Since "they" is acting as the subject here, the correct word to replace it would be "who." The correct choice is, "who."

This sentence misuses the word "it's." This form of the word "it" is a contraction for "it is." Since the word is meant to be possessive here, the correct form is "its," containing no apostrophe. No other changes are necessary. The correct choice is, "for the success or failure of its products."

This sentence misuses the word "its," which is the possessive form of the word "it." It is clear from context, however, that the contraction, "it's" is necessary here. The correct choice is, "It's important to study every day." The other choices do not contain legitimate forms of the word "it."

You can immediately cross out the answer choice with a gross error in both mechanics and grammar: "whos'". Using the relative pronoun "that" to describe a person is incorrect. In this case, the relationship between the noun "man" and the "dog" is one of ownership. We need to use the possessive relative pronoun "whose". All of the other answer choices incorrectly address these two points.

The central issue here is not verb tense usage but, rather, incorrect pronoun usage. "Who's" represents the contraction of the pronoun and verb "who is." The correct possessive form of the pronoun who is "whose." All of the other answer choices do not address this issue.

The correct answer will resolve the redundant relative pronoun that, replacing it with the definite article "the". Using the article "a" is problematic precisely because the article refers to a definite noun "the number of people...". The other answer choice that attempt to implement a subordinating conjunction all result in issues with awkward syntax.

This sentence misuses the word "who's," which is a contraction for "who is." The context of this sentence dictates that the possessive form of the word be used here. The correct choice is "whose." The other choices are not actual forms of this word.