96 Given $0 \leqslant \alpha \leqslant \beta<\gamma \leqslant 2 \pi$, and
$$
\cos \alpha+\cos \beta+\cos \gamma=0, \sin \alpha+\sin \beta+\sin \gamma=0
$$

then the value of $\beta-\alpha$ is
A. $\frac{\pi}{3}$
B. $\frac{2 \pi}{3}$
C. $\pi$
D. cannot be determined