Answer:
A, C
Step-by-step 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.