An adverb clause is defined exactly as it is in the question. It is used in a sentence to tell where, when, how, or to what extent something was done. It is similar to adverbs themselves, since adverbs also modify an adjective, verb, or another adverb based on time, place, degree, manner, etc.
A main clause is a clause that can stand alone on its own while an adjective clause will function as an adjective itself which answers either "how many?", "what kind?" or "which one?".
<span>A clause that tells how, when, where, or to what extent something was done is an adverb clause. The correct option among all the options that are given in the question is the first option or option "a". The other choices are incorrect. I hope that this is the answer that has come to your help.</span>
