Answer:
A. After the crew picked up the trash, they took a well-deserved break.
Step-by-step explanation:
A clause is a group of related words with at least a subject and a verb. An independent clause, in contrast to a dependent clause, always expresses a complete thought on its own and can be alone alone as a full sentence.
Sentence A is made up of a dependent clause: After the crew picked up the trash (this clause does not make much sense by itself), and an independent clause at the end: they took a well-deserved break, which does express a complete idea on its own, and thus, could stand alone as a full sentence with no problems.