\( f(x) \) অযুগ্ম ফাংশন হলে, \( \int_{-a}^{a} f(x) dx = ? \)

A \( \int_{0}^{a} [f(x) + f(-x)]dx \)

B \( \int_{0}^{a} [f(x) - f(-x)]dx \)

C \( 2 \int_{0}^{a} f(x) dx \)