The correct answer is A, WHEN THEY ARRIVED AT THE BEACH.
In English language, an adverb is one of the part of speech. An adverb is a part of speech that talk more or qualifies a verb. It can also be used to qualify an adjective, another adverb or a clause. An adverbial dependent clause refers to an adverbial clause that can not stand alone. In the question given above, the statement given in option A is an adverbial clause, which quality the verb 'arrived'.
Answer:
I think D is the best answer
Explanation:
