It has to be dilute since the crystal dissolved and unsaturated for the same reason so B
The answer to this question is 5
Answer: The frequency of the wave is 0.5 hertz.
Explanation:

= Frequency of the wave
= speed of the light in m/s
= Wavelength of the wave.
Here in question we are given with speed of the infrared light. So, we will replace the value of speed of light(c) from the given value of the speed of the infrared light.
Speed of infrared light = 6 m/s

The frequency of the wave is 0.5 hertz.
I think the answer is true.