Solve this following

Mark $(\sqrt{ })$ against the correct answer in the following:

$\int_{0}^{\pi / 2} \frac{\sin ^{4} x}{\left(\sin ^{4} x+\cos ^{4} x\right)} d x=?$

A. $\frac{\pi}{4}$

B. $\frac{\pi}{2}$

C. 1

D. 0