When a Parallel-Plate Capacitor of Capacitance C Is Connected to a Battery

Multiple Choice

When a parallel-plate capacitor of capacitance C is connected to a battery of voltage V, the energy density in the capacitor is u. If the voltage of battery is doubled, which of the following changes would keep the energy density equal to its previous value u?

A) doubling the spacing of the plates
B) doubling the size of the plates
C) reducing the size of the plates by half
D) reducing the spacing of the plates
E) The energy density is unaffected by a change in the voltage.