Use newton's second law to determine how much force is being applied to an object that is travelling at a constant velocity.

"Acceleration" is the rate at which velocity changes.

When you say "constant velocity", that's just another way to say
"zero acceleration".

Newton's second law says

               (Net force) = (mass) x (acceleration) .

So if acceleration is zero, then net force must also be zero.

Iagree c would be the answer