Explanation

(c) The direction of earth’s magnetic field is south to north. Torque on current carrying loop in a uniform magnetic field, $\overrightarrow{\tau} = \overrightarrow{M} \times \overrightarrow{B}$, which will rotate the coil. The loop will come to rest when torque is zero. It will be so if angle between $\overrightarrow{M}\ $ and $\overrightarrow{B}$ is zero. $ie,$ magnetic field is perpendicular to the plane of the coil. Therefore, the plane of the coil will be in east-west direction in equilibrium of rest.