A heavy rock and a light rock in free fall (zero air resistance) have the same acceleration. The reason the heavy rock doesn’t have a greater acceleration is that the (a) force due to gravity is the...

A heavy rock and a light rock in free fall (zero air resistance) have the same acceleration. The reason the heavy rock doesn’t have a greater acceleration is that the

(a) force due to gravity is the same on each.

(b) air resistance is always zero in free fall.

(c) inertia of both rocks is the same.

(d) ratio of force to mass is the same.

(e) none of these.