The use of the participle "working" as the verb in this sentence is incorrect, as a participle needs to be preceded by some form of the verb "to be" in order to function as the verb of a sentence. Either the verb needs to be changed to a workable verb, a form of "to be" needs to be inserted into the sentence right before it. The only answer choice that does either is "worked under an immense amount of pressure," which uses a simple past tense verb.

The use of the participle "reacting" makes the sentence actually have no proper verb, as a participle needs to be preceded by a form of the verb "to be." Either the verb form needs to be changed, or some version of the verb "to be" needs to be added into the sentence to make the sentence have a usable verb. The only answer choice that addresses this problem, by changing the participle to a past tense verb, is "reacted to their mother for the first time."

The use of the participle "baking" in the sentence means the sentence does not contain an actual verb. A participle needs to be preceded by some version of the verb "to be" in order to be a complete verbal phrase and act as a verb in a sentence. The only answer choice that makes such a change is "The grandmother was baking pies in the kitchen when everybody arrived."

The use of the participle "centering" as the verb in this sentence actually makes the sentence not have a verb, as a participle needs to be preceded by some form of the verb "to be" in order to function as a verb. The only answer choice that takes care of this problem, by changing the participle to a past tense verb, is "The group's biggest concerns centered on the political process itself."

The underlined portion needs to be improved by straightening out the verb "advocating." The verb tense in the final word needs to match with the use of "pay little attention" at the beginning of the sentence, which is in the present tense. "Candidates advocate" is the best choice among the answers.

The underlined portion of the sentence features an overwrought complex verb which also features an inappropriate verb usage. The use of "once" indicates the cars arrived in the past, so a past tense needs to be used. "Had arrived" is the best choice among the answers.

The issue in the sentence is with the verb "making." It is used not as the verb, but as a modifier of "designed;" therefore, it needs to take a form that can appropriately do so, such as an infinitive. "To make their opponents uneasy," is the best choice among the answers.

The use of the verb "learning" is incorrect in the sentence. The correct answer needs to feature an infinitive as the sentence describes a capacity of learning. "To learn as an adult" is the only grammatically correct answer choice.

The use of the phrase "Since the foundation of the club," indicates that the verb used in the underlined portion should be in the past tense. Additionally, the phrase needs to become a complete sentence on its own. "New members entered" is the only answer choice that fits both criteria.

The underlined words are a compound verb, or multiple words that function as one verb in the sentence. These still need to follow a correct tense and form, which is not done with just "having" being placed after people. "Have trouble focusing" is the best way to improve the sentences among the answer choices.