There are correlation and causation between the force of the finger and the movement of the books
The only answer that can justify being a hypothesis is C.
Explanation:
A wavefront is the long edge that moves, for example, the crest or the trough. Each point on the wavefront emits a semicircular wave that moves at the propagation speed v. These are drawn at a time t later, so that they have moved a distance s = vt.
882 divided by 9.81 (this is acceleration due to gravity) it equals 89.91
