When is a comma necessary to include with a date?

Read the sentences below and complete the instruction that follows. the coach, who has ten years' experience, has agreed to lead our team. the coach who has ten years' experience has agreed to lead our team. select the answer that explains the difference between the two sentences, as well as the purpose each clause serves for the benefit of the reader. a.) the first sentence contains a noun clause that functions as a predicate nominative; therefore, it renames the subject of the sentence for the reader. the second sentence contains an essential adjective clause that modifies the noun "coach"; therefore, it clarifies for the reader which coach is being discussed. b.) the first sentence contains a nonessential adjective clause that modifies the noun "coach"; therefore, it provides the reader with interesting details about the subject of the sentence. the second sentence contains an essential adjective clause that modifies the noun "coach"; therefore, it clarifies for the reader which coach is being discussed. c.) the first sentence contains a nonessential adjective clause that modifies the noun "coach"; therefore, it provides the reader with interesting details about the subject of the sentence. the second sentence contains a noun clause that functions as a predicate nominative; therefore, it renames the subject of the sentence for the reader. d.) the first sentence contains an adverb clause that modifies the verb "agreed"; therefore, it provides the reader with the answer to the question "when." the second sentence contains an essential adjective clause that modifies the noun "coach"; therefore, it clarifies for the reader which coach is being discussed.