To measure the magnetic moment of a bar magnet, one may use

A deflection or oscillation galvanometer can be used to know the magnetic moment of a bar magnet. For a deflection magnetometer, the formula to calculate moment is

And for a vibrational magnetometer is

Where, M is the magnetic moment, is the horizontal magnetic field, T is the time period.

Combining both equations, we can get rid of . Hence, B, C and D are true.