The answer is:
<u>Adverb clause:</u> whenever he is called.
<u>Subordinating conjunction:</u> whenever
<u>Word(s) modified:</u> responds
Adverb clauses consist of a group of words which function as an adverb. as a result, they modify a verb, adjective, another adverb or an entire sentence. They also contain a subject and a verb, and indicate when, where, how, why or under what condition the action of the verb happens.
Additionally, subordinating conjunctions join independent and dependent clauses. The first can stand on its own but the second cannot - it does not form a complete thought.
