In dynamics, the friction force acting on a moving object is always a) in the same direction of its motion b) a kinetic friction c) a static friction d) zero

B) a kinetic friction

Explanation:

The force of friction in a movement object its called kinetic friction force (fk). The net force acting in the direction of the movement its express, according to the Newton second law, like this: F - fk. That expression says that the net force produces an aceleration in the direction of the movement of the object.

Now if the force its removed, the fk its continue acting in the object but now in the opposite direction. And according to the Newton second law this fk it going to continue acting until the object stay in a still state.

In conclusion, if an object moves in some direction the kinetic friction force always be opposite to that direction of movement, according to the Newton second law