The total energy stored in a system of capacitors is the sum of the energies stored in individual capacitors. Based on the options, the capacitors are connected in parallel across the voltage $V$.

1. Energy in first capacitor ($C_1 = C$): $U_1 = \frac{1}{2} C_1 V^2 = \frac{1}{2} CV^2$
2. Energy in second capacitor ($C_2 = C/2$): $U_2 = \frac{1}{2} C_2 V^2 = \frac{1}{2} \left( \frac{C}{2} \right) V^2 = \frac{1}{4} CV^2$
3. Total Energy: $U_{\text{total}} = U_1 + U_2 = \frac{1}{2} CV^2 + \frac{1}{4} CV^2 = \frac{3}{4} CV^2$

Alternatively, for parallel combination, $C_{\text{eq}} = C + C/2 = 3C/2$. The total energy is $U = \frac{1}{2} C_{\text{eq}} V^2 = \frac{1}{2} (3C/2) V^2 = \frac{3}{4} CV^2$ [NCERT Class 12, Physics Part 1, Sec 2.15, Eq 2.69].