Answer:
Step-by-step explanation:
The answer is D.
A is the wavelength. As it says in its title, it shows the length of one complete wave.
B is the crest. This is the point in the wave where it's at its highest.
C is the trough. This is the point in the wave where it's at it's lowest.
And lastly, D is the equilibrium position. These are the points on the wave where they touch the equilibrium, or the horizontal line going through the wave.
