The correct answer is D. all of the above.
Mercury motor meters, commutator motor meters, and induction type single phase energy meters are all common forms of A.C. meters met with in every day domestic and industrial installations.
Mercury motor meters are the oldest type of A.C. meter and are still used in some applications. They work by using the rotation of a mercury-filled rotor to generate an electric current that is proportional to the amount of current flowing through the meter.
Commutator motor meters are a more modern type of A.C. meter that uses a rotating commutator to generate an electric current that is proportional to the amount of current flowing through the meter. They are more accurate than mercury motor meters and are less likely to be damaged by overloads.
Induction type single phase energy meters are the most common type of A.C. meter used in domestic and industrial installations. They work by using the principle of induction to generate an electric current that is proportional to the amount of current flowing through the meter. They are accurate, reliable, and relatively inexpensive.