Answer:
C.) π
Explanation:
Given function:

To find the period of the function.
Solution:
The general cosine function is given as:

where 
 represents the amplitude of the function and the period of the function is given as:
 represents the amplitude of the function and the period of the function is given as:
⇒ 

For the given function: 

The period is given as:
⇒ 

Cancelling the common terms, we have:
⇒ 

Thus, period of the given function = π