The correct answer to which clause from the sentence above is a dependent clause is option C) while I was reading last night.
A dependent clause is a group of words with a subject and predicate but that do not express a complete thought, so it cannot form or function syntactically as an independent sentence. It can be joined to another sentence to express a complete thought and function as an adverb, adjective or noun clause in a complex sentene.
In this case, <u>while I was reading last night</u> is the dependent clause because it cannot function as an independent sentence. We need more information about what happened while the speaker was reading last night. Thus, this clause is a dependent clause that functions as an adverbial phrase when combined with a main clause in a complex sentence.
