Answer:
Your answer would be that the sentence in which the underlined clause functions as an adverb clause is the following one: we can harness solar energy wherever the sun shines.
Step-by-step explanation:
Wherever the sun shines is an adverb clause. Adverb clauses, also known as adverbial clauses, are dependent clauses that function as adverbs. Since they are dependent clauses, they must have a subordinating conjunction to connect to the rest of the sentence. Dependent clauses fail to stand alone as a sentence because they do not represent a complete thought; they depend on the main clause to complete their meaning.
In this case, the subordinating conjunction introducing the adverb clause is wherever. This conjunction is adding information as regards time, when the event takes place.