The density of water is maximum at:

Options

A. `4^(@)C`
B. `gt 4^(@)C`
C. ` lt 4^(@)C`
D. `10^(@)C`

Explanation

To determine the temperature at which the density of water is maximum, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Density and Temperature Relationship**:
- Generally, for most substances, as the temperature increases, the density decreases. This is because an increase in temperature typically causes an increase in volume, leading to a decrease in density (Density = Mass/Volume).

2. **Behavior of Water**:
- Water exhibits a unique behavior compared to most substances. As the temperature of water increases from 0°C to 4°C, its density actually increases. This is contrary to the general trend observed in other substances.

3. **Identifying the Maximum Density**:
- At 4°C, water reaches its maximum density. This is a critical point because, beyond this temperature (i.e., from 4°C to higher temperatures), the density of water begins to decrease as the volume increases with further heating.

4. **Anomalous Expansion of Water**:
- The phenomenon where water behaves differently (increasing density with increasing temperature up to 4°C) is known as the anomalous expansion of water. This is largely due to the hydrogen bonding between water molecules, which affects how they arrange themselves as temperature changes.

5. **Conclusion**:
- Therefore, the density of water is maximum at **4°C**.

### Final Answer:
The density of water is maximum at **4°C**.

---