A wave pulse happens when a wave travels through a medium from one end to the other. The wave pulse causes the medium to move up and down as it travels through the medium, but it does not cause the medium to be moved from one end to the other. Draco creates a wave pulse in a spring by moving one end of the spring up and down. The picture below shows the wave pulse moving from one end of the spring to the other.

Draco is going to create another wave pulse by moving the spring up and down again. Which of these must be true if he moves the spring up and down more slowly the next time?
A.
The wave pulse will be shorter.
B.
The wave pulse will be higher.
C.
The wave pulse will be longer.
D.
The wave pulse will travel faster.