On a warm summer day, a group of friends went swimming at the pool. They experienced hot, humid air at noon; but a few hours later the temperature dropped, and a thunderstorm occurred. Which explanation below BEST describes what caused this event? A.
A warm air mass moved in, pushing the hot, humid air up, creating a warm front.

B.
A cool air mass moved in pushing the hot, humid air up, creating a cold front.

C.
A warm air mass moved in, pushing the hot, humid air up, creating a cold front.

D.
A cool air mass moved in pushing the hot, humid air up, creating a warm front.