Answer:
D. Most animals thrive where they can find food easily.
Step-by-step explanation:
An adverb clause is a dependent clause, that is to say, a group of related words that have at least a subject and a verb and that can not stand alone as a sentence because it does not express a complete thought. Its primary function is to act as an adverb: it modifies adjectives, verbs or other adverbs; and we can easily identify them in sentences because they often answer questions such as "Why?", "How?", "When?", "Where?" or "In what circumstances?".
In the sentence, there is an independent clause (A clause that can stand on its own because it expresses a complete thought): "Most animals thrive" and a dependent clause: "where they can find food easily." The latter is an adverbial clause because it modifies or gives further information of the verb "thrive", and can be answered with the "where" question: "Where do most animals thrive?" Answer: "Where they can find food easily."