Stan Sweats Profusely When He Works Out at His College's

Stan sweats profusely when he works out at his college's weight room, even though the facility is always very cool inside. Why is this?

A) Stan has a high metabolism that causes him to perspire all the time
B) Stan's working muscles give off a lot of heat, which must then be released
C) Stan drinks too much water during his workouts
D) Stan's plasma volume must be maintained at an appropriate level