1. Capacitors in parallel

   If there are $n$ identical capacitors, each of capacitance $C$, connected in parallel, then the equivalent capacitance is

   $C_{\text{eq}} = nC$

2. Energy stored in a capacitor combination

   The energy stored in a capacitor is given by

   $U = \frac{1}{2} C V^2$

   So for the equivalent capacitance $C_{\text{eq}} = nC$ connected across a voltage $V$,

   $U = \frac{1}{2} C_{\text{eq}} V^2$

3. Substitute $C_{\text{eq}} = nC$

   $U = \frac{1}{2}(nC)V^2 = \frac{1}{2} n C V^2$

4. Match with the options

   • A: $CV$ — incorrect, wrong formula and wrong dimensions
   • B: $\frac{1}{2}nCV^2$ — correct
   • C: $CV^2$ — missing factor $\frac{1}{2}$ and $n$
   • D: $\frac{1}{2n}CV^2$ — incorrect

Therefore, the correct answer is B.