A weak acid HA has a $K_a$ of $1.00 \times 10^{-5}$. If $0.100\; mol$ of this acid is dissolved in one litre of water the percentage of acid dissociated at equilibrium is closest to :

Question

( A ) $99.9 \%$
( B ) $0.100 \%$
( C ) $1.00 \%$
( D ) $99.0 \%$