I would say B but I’m not 100%
I believe the term Frequency is what you are looking for.
Answer:
Potential Energy to Kenetic Energy
Explanation:
When holding a ball in the air, the ball has potential energy. Once you drop the ball, the ball gains Kenetic Energy
Answer:
Velocity, v = 0.239 m/s
Explanation:
Given that,
The distance between two consecutive nodes of a standing wave is 20.9 cm = 0.209 m
The hand generating the pulses moves up and down through a complete cycle 2.57 times every 4.47 s.
For a standing wave, the distance between two consecutive nodes is equal to half of the wavelength.

Frequency is number of cycles per unit time.

Now we can find the velocity of the wave.
Velocity = frequency × wavelength
v = 0.574 × 0.418
v = 0.239 m/s
So, the velocity of the wave is 0.239 m/s.
By giving them an advice and by giving them encouraging and explaining the any theory