John and Angie were each pushing a box across the floor. They both push their own box with a force of 30 Newtons; however, Angie's box does not move. What can you infer is the reason Angie's box didn't move?
A) No work was done on the box.
B) Gravity did not act on the box.
C) John's box might have been on an incline.
D) She was probably smaller than John so she didn't have enough strength to move the box.