A lump of ice has a temperature of $-100^{\circ}\text{C}$. It is heated at a steady rate of energy input. The graph illustrates how the temperature varies. At which points has all the ice fully become water and all the water fully become steam?
- Acompletely changed to water: $1$, completely changed to steam: $3$
- Bcompletely changed to water: $1$, completely changed to steam: $4$
- Ccompletely changed to water: $2$, completely changed to steam: $3$
- Dcompletely changed to water: $2$, completely changed to steam: $4$