The correct answer is B, "Today's dig laster longer than the one yesterday."
An adverb clause is a dependent clause that usually modifies a verb, but can also modify an adjective or another adverb. Adverb clauses are usually introduced using words including: after, although, as, as if, before, because, if, since, so that, than, though, unless, until, when, where, and while. In this cause, the adverb clause is introduced by the word than.