$8.$A capacitor charged to $1\mathrm{.}5$ V stores $2\mathrm{.}0$ mJ of energy. If the capacitor is charged to $3\mathrm{.}0$ V $,$ it will store

A$.1\mathrm{.}0$ mJ

B$.2\mathrm{.}0$ mJ

C $4\mathrm{.}0$ mJ

D$.6\mathrm{.}0$ mJ

$(3)8\mathrm{.}0m.J$