What advice would you give her to improve her diagram? Choose all that
apply.

A, C

Explanation:

In order for a box to be moving at constant velocity, that means acceleration must be 0(as the speed isn't increasing). Thus, since F = ma, and a is 0, the net force must also be 0. The diagram must be completely balanced in every direction, which is why the two horizontal arrows must be equal values.

C is also true because gravity is a stronger force here than the applied force. We can calculate the force due to gravity with Fgravity = mg. Thus, we get the force as a result of gravity = 9.8*50, which is around 500N and much larger than the applied force of 200N.

the higher the current the higher the mag field around it the higher the influence on the compass