When an AC voltag

Option(a):

When we say voltage in ac circuit, we mean rms voltage and not maximum voltage. Hence, (a) is wrong.

Option(b):

In a capacitor, current leads the voltage by 90°. Hence, they are not in phase. This option is wrong.

Option(c):

The amount of charge in the capacitor is proportional to the voltage across it at any given time. Now, the instantaneous voltage across the capacitor is the same as that supplied by the source Hence, the charge is in phase with the voltage. Hence, this option is correct.

Option (d):

Note that

Now, for a purely inductive or capacitive circuit, R = 0.

Hence,

A capacitor doesn’t lose energy to heat etc.; it stores energy. It makes sense for the power to be zero. Thus, (d) is correct.