Answer: The frequency of the wheel's rotation is 0.5 Hz.
Step-by-step explanation:
Frequency of rotation: It is defined as the number of revolution in a second.
The expression for the frequency in terms of the number of revolution in a given time is as follows;

Here N is the number of cycles and t is the time taken.
Put N= 2 rev and t= 4 s in the above expression.


Therefore, the correct answer is 0.5 Hz.