Final answer:
The closest antonym for the word 'prolific' is 'sparse,' as it means thinly dispersed or scattered, which is opposite to abundant or plentiful, which is what 'prolific' implies.
Therefore, option C is correct.
Step-by-step explanation:
The closest antonym for the word prolific is sparse. Prolific means producing a lot or being fruitful, typically used to describe a high output of work, abundant creativity, or a large number of offspring. On the other hand, sparse means thinly dispersed or scattered, which is the opposite of being abundant or plentiful. Therefore, out of the provided options, sparse is the antonym that is most opposite in meaning to prolific.
Options A (Ingenious) and D (Excessive) are not antonyms. Ingenious refers to showing creativity or inventiveness, while excessive means more than necessary. Option B (Consistent) relates to uniformity or reliability over time, which is also not an antonym for prolific.