Answer:
4 Hz
5 m
1 m
20 m/s
Step-by-step explanation:
The first part of the sentence describes the frequency of the wave i.e., the number of oscillations every second
f = 4 /s = 4 Hz
The second part of the sentence describes the wavelength or period of the wave i.e., the distance between successive crests or troughs.
λ = 5 m
The last part of the sentence describes the peak to peak amplitude of the wave i.e., the height between the lowest part to highest part of the wave

The peak amplitude is given by

The velocity of a wave is given by
v = fλ
⇒v = 4×5
⇒v = 20 m/s
The velocity of the wave is 20 m/s