The capacitance of the system is C. If the key is closed, the total energy loss is equal to

• A

  $\frac{{\mathrm{Q}}^2}{2\mathrm{C}}$

• B

  $\frac{2{\mathrm{Q}}^2}{\mathrm{C}}$

• C

  $\frac{9{\mathrm{Q}}^2}{8\mathrm{C}}$

• D

  none of these