The solubility product of a salt having general formula $MX_2$, in water is $4 \times 10^{-12}$. The concentration od $M^{2+}$ ions in the aqueous solution of the salt is :

Question

( A ) $2.0 \times 10^{-6} M$
( B ) $4.0 \times 10^{-10} M$
( C ) $1.0 \times 10^{-4} M$
( D ) $1.6 \times 10^{-4} M$