Pls answer if u know the answer ^w^ thx! Friction .

A) is always and unwanted force

B) works in the opposite direction of motion

C) causes machines to work 100 percent efficiently

D) can be increased using lubricants, like oil

works in the opposite direction of motion

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                                         : )

gas and liquid