Respuesta :
The answer, in my opinion, is the second sentence, "The coach who is an expert in the sport explained the revised rules to us". Here, the "Who is an expert", is presumably the nonessential clause.
Answer:
B. The coach who is an expert in the sport explained the revised rules to us.
Explanation:
The adjective clause exemplifies the modifier of the noun clause that contains both a subject and a verb and begins with a relative pronoun. The sentence contains a nonessential adjective clause is the second option. It carries unnecessary adjective clause, i.e. "who is an expert in the sport" as it describes the coach unreasonably. If he is a coach, the description mentioned here is quite obvious and understood. Thus, it is not required to mention it. Hence, the B option is the answer.