Answer:
C). If you visit Pennsylvania, take the self-guided, covered-bridge tour.
Explanation:
An adverb clause consists of a subject and a verb and begins with subordinating conjunction like if, although, because, etc. It functions as an adverb in a sentence and modifies a verb, adjective or adverb in the sentence that adds significant description and information to a sentence. According to this question, the sentence that employs an adverbial clause "If you visit Pennsylvania" in it, so, it is option C as it meets and justifies all the descriptions and claims as mentioned above. It begins with 'if'(subordinating conjunction), subject(You) and verb(visit) and adding a description to the sentence. Thus, option C is the correct answer.
