The answer to your question would be that the sentence that contains an adverb clause is the following one: When you return from California, take a taxicab from the airport. That is, the correct option would be B.
An adverb clause is a dependent clause that functions as an adverb in a sentence. As they are dependent clauses, they must have a subordinating conjunction connecting them to the rest of the sentence. In this case, the subordinating conjunction "when" is the one that introduces the adverb clause. It gives information about the time in which you should take the taxicab from the airport.
