A train is moving along a straight section of the track at a constant speed. Which of the following statements about the train is true. a). If the train is moving at a constant speed, there must be no forces at all acting on the train.

b). If the train is moving at a constant speed, then any forces that might be acting on the train must cancel out.

P. s-The subject is actually science topic: forces review

c). There must be an unbalanced force acting on the train to keep it moving.

d). The train must have a force acting on it larger than the train's inertia in order to keep moving.