Answer:
b. speed of a wave
Explanation:
The speed of a wave is defined as the product between the wave's frequency and the wave's wavelength:
[tex]v=\lambda f[/tex]
where
[tex]\lambda[/tex] is the wavelength of the wave
f is the frequency
Therefore, we see that this matches the definition listed in choice B:
b. speed of the wave.
The other options are:
a. number of waves passing a point in a second. --> frequency
c. distance between wave crests. --> wavelength
d. time for one full wave to pass. --> period
