Answer:
The detail, "And someone gave little Davy Hutchinson a few pebbles", contributes to the text because his mother was the one being stoned, but the person who gave him some pebbles was suggesting that he needed to start participating at a young age, just as everyone else did.
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'.
Atticus Finch believes that Mrs. Dubose is the bravest person he knows.