Answer:
Adverb clause.
Step-by-step explanation:
An adverb clause is a clause or group of words that can be used or functioning as an adverb in a given sentence. It modifies the verb or adverb or adjective in the sentence thereby giving extra information about the where, why, how, when, etc of the verb.
As given in the question, the subordinate clause is "while talking". This subordinate clause needed an independent clause to be able to function as a complete meaningful sentence. This subordinate clause modifies or affects the verb "waved" which makes it an adverb clause.
Thus, the correct answer is the adverb clause.