A galvanometer can be converted into an ammeter by connecting a shunt resistance in parallel to it.
The shunt resistance should have very low resistance. So, the ammeter (the parallel combination of galvanometer and shunt resistance) will have low resistance.
To convert a galvanometer into an ammeter of current rating ‘I’, a small resistance ‘S’ (shunt resistance) is connected in parallel across the galvanometer.
Vg=(I−Ig)S=IgRg Where Vg is the voltage across the galvanometer, I is current in the circuit, Ig is the current is galvanometer, Rg is the resistance of galvanometer and S is the resistance of the shunt.
EXPLANATION:
A moving coil galvanometer can be converted into a ammeter by connecting a low resistance in in parallel to the moving coil galvanometer. So option 2 is correct.