Earthing (grounding) connects the exposed metal parts of an appliance to the earth through a low-resistance conductor. Its purpose is to provide a safe, deliberate path for any fault (leakage) current, so that under a fault the metal body stays close to earth potential and the large fault current trips the fuse or circuit breaker.

Consider what happens in a non-earthed device when a fault develops (for example, the insulation on the live wire breaks and the live conductor touches the metal casing):

• With no earth connection, there is no low-resistance path to ground to carry the fault current away.
• The metal enclosure therefore rises to the supply (live) potential — around 230–240 V in India.
• If a person standing on the ground (at earth potential) touches the casing, their body completes the circuit to earth, and a dangerous, possibly fatal, current flows through them.

Hence the correct outcome is that the exposed metal parts may carry a dangerous voltage.

The other options are incorrect: a fault does not change the resistance of the device in any meaningful protective way; without a fault current large enough to blow the fuse there is nothing to automatically shut the device down (indeed, the hazard is precisely that it keeps running while live), and the supply voltage does not decrease — the enclosure actually becomes energised at supply potential.