The area of the region described by A={$(x,y):(x^2+y^2\leq 1$ and $y^2\leq 1-x$}
$\begin{array}{1 1}(A)\;\large\frac{\pi}{2}+\frac{4}{3}\\(B)\;\large\frac{\pi}{2}-\frac{4}{3}\\(C)\;\large\frac{\pi}{2}-\frac{2}{3}\\(D)\;\large\frac{\pi}{2}+\frac{2}{3}\end{array}$