pH of a saturated solution of $Ca(OH)_2$ is 9. The solubility product $(K_{sp}) $of $Ca(OH)_2$ is :-

Question

( A ) $0.5 \times10^{–10}$
( B ) $0.125\times 10^{–15}$
( C ) $0.5\times 10^{–15}$
( D ) $0.25 \times10^{–10}$