Answer: The correct answer is 0.11 Hz.
Step-by-step explanation:
The relation between frequency of the wave and time period is as follows;

Here, f is the frequency of the wave and T is the time period.
Here, the frequency is inversely proportional to the time period.
It is given in the problem that a wave has a wavelength of 45 meters and a period of 9.0 seconds.
Calculate the frequency of the wave.

Put T= 9 s.

f=0.11 Hz
Therefore, the frequency of the wave is 0.11 Hz.