The product of the frequency and the wavelength of a wave equals the

a. number of waves passing a point in a second.
b. speed of the wave.
c. distance between wave crests.
d. time for one full wave to pass.

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:

where

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

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

i believe the answer is a hope it and is correct