Certain galvanometers have a fixed core made of non magnetic metallic material. The function of this metallic material is

In a moving coil galvanometer, a fixed core made of non-magnetic metallic material (such as soft iron) serves an important purpose.

When the coil rotates in the magnetic field, the metallic core has eddy currents induced in it. These eddy currents produce a damping effect (electromagnetic damping) that opposes the motion of the coil, bringing it to rest quickly without prolonged oscillation. This is known as "dead-beat" behavior.

This quick damping allows the galvanometer needle to settle rapidly to the correct reading, rather than oscillating back and forth around the equilibrium position.

The answer is Option B: to bring the coil to rest quickly.