The word "authoritative" means trustworthy or self-assured and commanding . So, the best answer choice is "commanding."" "Power" is not the best choice because it is a noun that refers to the strength of something. Since "authoritative" is an adjective, the answer must also be an adjective.

"Dominant" means in control, in charge, on top.

"Influential" means having a powerful effect on people or events. "Important," which means significant or valuable, is closest in meaning to "influential," so it is the correct answer.

Incorrect answers:

"Miraculous" means inexplicable or occurring through or as if through divine intervention, as in the sentence, "The sick child made a miraculous recovery that the doctors did not think was possible."

"Approving" means thinking favorably of, as in the sentence, "The teacher had an approving look on her face as she told the students she was proud of their hard work."

"Cautious" means careful, as in the sentence, "You must be cautious when you cross the busy street."

The word "infinite" actually means not finite. Now, if something is called "finite" it is measurable. In other words, it "comes to an end." Thus, even though a billion is a large number, a billion dollars is finite. You can eventually "come to an end" when counting it; however, something "infinite" is endless. For example, there are an infinite number of numbers when you count. You can always keep counting one number higher. Thus, the best option is "limitless" meaning "having no limit" or "having no endpoint."

"Feeble" means weak or ineffectual. To further help you, "robust," "sturdy," and "brawny" are synonyms and all mean strong.

When something is "necessary," it must be done. For instance, some people say that it is necessary to good health that we exercise at least five days a week. This means that good health requires such activity. Likewise, it is required that you have a large vocabulary to do well on the ISEE verbal sections. This means that you need to have a large vocabulary to do well. Therefore, something that is "required" is something that has been said to be necessary. "Requirements" are necessary things to be done or things that are needed. (The requirements for an application are all of its necessary components.)

The word "trivial" means unimportant. "Unimportant" is the best choice because it is a part of the definition of "trivial."

"Major" means important.

When a person is "illustrious," he or she is widely admired or respected, usually for his or her accomplishments. This word could describe a professor who published many groundbreaking papers, or a well-liked athlete with a long and successful career. "Respected" is the correct synonym here. "Arid" refers to climate conditions that are unusually dry, while neither "playful," "sincere," or "abnormal" properly captures the admiration implied by this term.

The word "ferocious" is related to the word "fierce." This can mean extreme, as when we say, "There was a fierce storm last night." This means that the storm was strong. Often "ferocious" is used to describe animals that are very fierce and dangerous. Thus, it can also mean "wild." For example, to say, "The ferocious dog bit the burglar's leg and would not let go," means that the dog was fierce in its attack on the burglar.