1. Identify the process

A block of ice at $-10^\circ\mathrm{C}$ is heated slowly until it becomes steam at $100^\circ\mathrm{C}$. The heating happens in stages:

• Ice warms from $-10^\circ\mathrm{C}$ to $0^\circ\mathrm{C}$
• Ice melts at $0^\circ\mathrm{C}$
• Water warms from $0^\circ\mathrm{C}$ to $100^\circ\mathrm{C}$
• Water vaporizes at $100^\circ\mathrm{C}$

So the temperature vs heat supplied curve must have two rising parts and two horizontal parts.

2. Stage-wise behavior

Stage 1: Heating ice

Temperature rises from $-10^\circ\mathrm{C}$ to $0^\circ\mathrm{C}$.

$Q = m s_{\text{ice}} \Delta T$

So temperature increases linearly with heat supplied.

Stage 2: Melting at $0^\circ\mathrm{C}$

Temperature remains constant while latent heat of fusion is absorbed.

$Q = mL_f$

So the graph is horizontal at $0^\circ\mathrm{C}$.

Stage 3: Heating water

Temperature rises from $0^\circ\mathrm{C}$ to $100^\circ\mathrm{C}$.

$Q = m s_{\text{water}} \Delta T$

Again, temperature increases linearly with heat supplied.

Stage 4: Vaporization at $100^\circ\mathrm{C}$

Temperature remains constant while latent heat of vaporization is absorbed.

$Q = mL_v$

So the graph is horizontal at $100^\circ\mathrm{C}$.

3. Qualitative shape required

Thus the correct curve must show:

1. Increasing temperature from $-10^\circ\mathrm{C}$ to $0^\circ\mathrm{C}$
2. Horizontal segment at $0^\circ\mathrm{C}$
3. Increasing temperature from $0^\circ\mathrm{C}$ to $100^\circ\mathrm{C}$
4. Horizontal segment at $100^\circ\mathrm{C}$

This is the standard heating curve of water.

4. Choosing the option

Among the given options, the one representing this qualitative behavior is Option A.

5. Comparison with stored answer

Stored correct answer: A

Derived answer: A

They match.