The correct option is D 12QV
By energy stored in a charged conductor Suppose, a conductor of capacity C is charged to a potential V and Q the charge on conductor at a instant.
The potential of the conductor
V=QC
Now, work done in bringing a small charge dQ at this potential is,
dW=vdQ=QCdQ
∴ Total work done in charging it from 0 to Q is,
W=∫Q0dW=∫Q0QCdQ
=12Q2C
This work is stored as the potential energy.
U=12Q2C (∵Q=VC)
U=12CV2=12QV