Correct Answer: D

Rationale: The sentence 'He runs fast' uses 'fast' correctly as an adverb. An adverb is used to describe a verb and in this case, 'fast' is describing how 'he runs.' Choices A, B, and C use 'fast' as an adjective, not an adverb. In choice A, 'fast' is describing the car, in choice B it is describing how the car drove, and in choice C it is describing the runner.

Correct Answer: B

Rationale: The correct answer is B: 'Sluggish.' Torpid means being slow or inactive. Choice A, 'Energetic,' is the opposite of torpid. Choice C, 'Fast,' is not synonymous with torpid as it refers to quickness rather than sluggishness. Choice D, 'Slow,' is somewhat related to torpid but does not fully capture the inactive aspect of the term.

Correct Answer: C

Rationale: "Pondering" is another word for contemplating because it means to think about something carefully or thoroughly. Both terms imply deep reflection or consideration of a subject or idea. Therefore, "pondering" best captures the meaning of contemplating among the given choices.

Correct Answer: B

Rationale: The correct answer is B, 'Wide open'. Gaping refers to something being wide open, not partially closed (choice A), narrow (choice C), or sealed (choice D). In the context of the question, 'Gaping' describes something that is open widely.

Correct Answer: A

Rationale: A prefix is the correct answer. A prefix is a word part attached at the beginning of a word to modify its root word, changing the definition or grammatical function of the word. Examples of prefixes include "un-" in "unhappy," "re-" in "redo," and "pre-" in "preview." Choice B, "Affix," is incorrect because while a prefix is a type of affix, not all affixes are prefixes. Choice C, "Suffix," is incorrect as a suffix is a word part added at the end of a word to change its meaning. Choice D, "Vocab," is incorrect as it refers to vocabulary or words related to a particular subject rather than a word part placed before a word.