The word "vital" means absolutely necessary. "Necessary" is the best choice because it is a part of the definition of "vital."

The word "significant" means important. The best choice is "important," as it is a part of the definition of "significant." Considering the other choices, "focus," when used as a noun, means center point, careful attention, or concentration, a "sign" is a notice that bears a message, and "combined" means joined together.

Something that is essential is needed; it is something you cannot do without. To further help you, irate means very angry; compassionate means loving; edible means able to be eaten; visible means able to be seen.

"Absolute" is defined as unquestionable, such as when describing a king’s absolute authority. The best match, "supreme," means having the final (unquestionable) say in things or of the highest rank in some category. So, "supreme" is the correct answer.

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.)

"Major" means important.

The correct answer is "harsh." Both "severe" and "harsh" mean strict or having no leniency. The other words mean the opposite of "strict."

Something that is "smothering" is excessive to the point of causing discomfort. Something that is "overbearing"  imposes too much. "Overbearing" is the most similar to "smothering" because both refer to the characteristic of being too invasive. 

The word "minor" comes from the Latin for smaller or less. We use the word in many ways, but they generally mean small or less in a given respect. Sometimes, the word "minor" is used as a noun to describe a person who is young and not yet an adult. As an adjective, it basically means small or not important. A "minor wound" is one that is not very large, and a "minor error" is one that is not very important. When something is "insignificant," it is not of great importance. A "significant" event, on the other hand, is one that is very important. While "minor affairs" might be "dull," the word "minor" primarily indicates being unimportant or small. Therefore, "insignificant" is the best option among those provided for you in the answers.

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.