Answer:
The correct option is a.
Explanation:
The given expression is

Let the value of the given expression in radian be θ.


Since the value of sinθ is 0, therefore the value of θ is in the form of

Where n can be any integer.
At n=0, the value of θ is 0, therefore the option a is correct.
Since n is an integer, therefore the coefficient of π can not be a fraction value.