the floor the pull of gravity the air friction on the ball the person that throws the ball
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: A ball is thrown downward onto a concrete floor and bounces upward. What supplies the upward force that makes the ball bounce?
Possibilities:
- the floor
- the pull of gravity
- the air friction on the ball
- the person that throws the ball

the floor