As the voltage in an ac circuit fluctuates, we measure it by its root mean square value. V_rms is mathematically represented as . The meter measuring AC voltage reads the rms voltage. Hence, correct option is (c).

Option (a) is wrong because it is given that the source is AC. Hence, we can only have AC voltage.

The meter doesn’t show the maximum voltage. Hence, option (b) is wrong.

There is no reason there should be a mechanical defect. In fact, for household use, the rms voltage of the ac current coming through the power lines is 220V in India. Hence, option (d) is incorrect.