If you were writing an essay arguing that swimming is one of the best exercises a person can do to build muscles, which reason would be relevant to that argument?
NOTE: Relevant means 'closely connected.'

A) Swimming is lots of fun to do, and it cools you off.
B) Swimming can be done in a pool, a river, a lake, or an ocean.
C) Swimming is not an expensive sport that requires buying lots of equipment.
D) Swimming works out every major muscle group of the body.