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:
⇒

For the given function:

The period is given as:
⇒

Cancelling the common terms, we have:
⇒

Thus, period of the given function = π