A block of ice has a temperature of $-100\,^\circ\text{C}$. Heat is provided at a steady rate. The graph indicates how its temperature varies. At which points has all the ice fully changed into water and all the water fully changed into steam?
- Awater at $1$, steam at $3$
- Bwater at $1$, steam at $4$
- Cwater at $2$, steam at $3$
- Dwater at $2$, steam at $4$