Answer:
Protons and neutrons are all attracted to each other as a result - the strong nuclear force. This is an attractive force that only has an effect over a very short range in the nucleus.
(a) Period of the wave
The period of a wave is the time needed for a complete cycle of the wave to pass through a certain point.
So, if an entire cycle of the wave passes through the given location in 5.0 seconds, this means that the period is equal to 5.0 s: T=5.0 s.
(b) Frequency of the wave
The frequency of a wave is defined as

since in our problem the period is

, the frequency is

(c) Speed of the wave
The speed of a wave is given by the following relationship between frequency f and wavelength

:
I think it is D. I hope this helps