The correct answer is B. Dr. Robert Garcia.
Given that this entire excerpt is written based on this author's study, it would be best to hyperlink his name so as to go to his study and check the original source of information. Placing it elsewhere wouldn't really make any sense at all.
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'.
I would say B, it makes the most sense out of those
Can you be more specific with your question I don’t think we understand
