A. that she couldn't catch her breath/fast
EXPLANATION
An adverbial clause is a dependent clause that functions as an adverb; that is, the entire clause modifies a verb, an adjective, or another adverb.
In the example, the adverb clauses "that she couldn't catch her breath" and "fast" modifies the verb "run".
As with all clauses, an adverb clause contains a subject and predicate, although the subject as well as the verb may sometimes be omitted and implied.
