Number of $H^+$ ions in 100ml of 0.001M $H_2SO_4$ is

Question

$\begin{array}{1 1}(a)\;6\times 10^{20}&(b)\;1.2\times 10^{18}\\(c)\;12\times 10^{18}&(d)\;1.2\times 10^{20}\end{array}$