What cloud type signals the coming of a warm front? (I don't think it's physics but I couldn't find a subject that fit)

altocumulus, cirrocumulus and cumulonimbus are cloud types that signals a warm front

Explanation:

The subject is geography

answer would be letter choice (a),   a ball resting on a shelf. would be another example of potential energy   >   stored energy > not moving.

a ball spinning on a finger   >   kinetic energy > moving energy

a ball rolling on the ground   >   kinetic energy   > moving energy

a   ball flying through the air   > kinetic energy   >   moving energy

hope that                                         : )