Correct Answer - A
The change of ice at `10^(@)C` into steam at `100^(@)C` occurs in four stages , it is repersented by curve (a).
`I` stage - The temperature of ice change from `-10^(@)C` to `0^(@)C`
`II` Stage - Ice at `0^(@)C` changes in water at `0^(@)C`. The state changes as heat is supplied.
`III` Stage- Water at `0^(@)C` changes into water at `100^(@)C`.
`IV` Stage- Water at `100^(@)C` change into steam at `100^(@)C`.