Question

what unbalanced force causes a skateboard to stop rolling on a flat surface? inertia mass friction gravity

Explanation:

Inertia is the tendency of an object to resist changes in its state of motion. Mass is a measure of the amount of matter in an object. Gravity is the force that attracts objects towards each other. Friction is a force that opposes the relative motion between two surfaces in contact. When a skateboard rolls on a flat surface, the friction between the wheels and the surface acts against the motion of the skateboard, causing it to slow down and eventually stop.

Answer:

C. Friction