The graph represents the simple harmonic motion of a pendulum. A graph with displacement on the y axis and time on the x axis. There is a transverse wave form drawn from the y axis toward the right with the x axis at the equilibrium position of the wave. The top of the first crest os labeled A. The distance from the first trough to the second trough is labeled C. The height of the second crest is labeled B. The distance from the top of the crest to the bottom of the trough is labeled D.
Which arrow indicates the period of the motion?

A
B
C
D