It’s the crest, the crest is the top part of the wave and the trough is the bottom so they correspond
Answer:
B
Explanation:
It's Scientifically proven
Im pretty sure its the first option
In order to draw the free body diagram, first let's calculate the friction force acting on the crate:

Since the friction force is greater than the force applied, the crate will not move, and the friction force will be equal to the force applied.
The weight force is equal to 40 * 9.8 = 392 N.
So, drawing the diagram, we have: