A body floats at 4°C water. If temperature reaches 100°C, then

The key to understanding this lies in how water's density changes with temperature.
Water has a unique property: Its density is maximum at 4°C.
When water is at 4°C, it's at its densest.
As the temperature increases from 4°C to 100°C, the density of water decreases.

Archimedes' Principle: A body floats when the buoyant force (upward force exerted by the fluid) equals the weight of the body.
The buoyant force depends on the volume of fluid displaced and the density of the fluid.

Since the water density decreases when heated to 100°C, a larger volume of water needs to be displaced to provide the same buoyant force to support the body's weight.
Therefore, more of the body will submerge to displace the necessary volume of the less dense (warmer) water.
So, the correct answer is (C).