The volume of a solid generated by rotating the region between semi-circle $y=1-\sqrt{1-x^{2}}$ and straight line $y=1,$ about $x$ axis, is
(A) $\pi^{2}-\frac{4}{3} \pi$
(B) $4 \pi^{2}-\frac{1}{3} \pi$
(C) $\pi^{2}-\frac{3}{4} \pi$
(D) $\frac{3}{4} \pi^{2}-\pi$
The volume of a solid generated by rotating the region between semi-circle $y=1-\sqrt{1-x^{2}}$ and straight line $y=1,$ about $x$ axis, is
(A) $\pi^{2}-\frac{4}{3} \pi$
(B) $4 \pi^{2}-\frac{1}{3} \pi$
(C) $\pi^{2}-\frac{3}{4} \pi$
(D) $\frac{3}{4} \pi^{2}-\pi$