Answer:
The choice that best describes the purpose of the underlined adverbial clause in the sentence is B. The adverbial clause indicates reason.
Explanation:
Adverb clauses, also called adverbial clauses, are dependent clauses that function as adverbs. As they are dependent clauses, they must have a a subordinating conjunction to connect them to the rest of the sentence. In the sentence above, the subordinating conjunction introducing the adverbial clause is because. It gives information as regards the reason why the speaker decided to wait in the long line.
