The metal which reacts with water at room temperature is

Options

A. Copper
B. Iron
C. Magnesium
D. Sodium

Explanation

To determine the metal that reacts with water at room temperature, we can analyze the properties of various metals and their reactivity with water.

### Step-by-Step Solution:

1. **Identify Common Metals**: Consider common metals that are known for their reactivity with water. Some of these include sodium, potassium, calcium, and magnesium.

2. **Analyze Reactivity with Water**:
- **Sodium (Na)**: Sodium is a highly reactive alkali metal that reacts vigorously with water at room temperature, producing sodium hydroxide and hydrogen gas.
- **Potassium (K)**: Potassium also reacts with water at room temperature, even more vigorously than sodium.
- **Calcium (Ca)**: Calcium reacts with water, but the reaction is less vigorous compared to sodium and potassium.
- **Magnesium (Mg)**: Magnesium reacts with water, but this reaction is very slow at room temperature; it typically requires steam for a significant reaction.

3. **Consider Other Metals**: Metals like copper, iron, and aluminum do not react with water at room temperature. Copper does not react at all, while iron reacts only with steam.

4. **Conclusion**: Among the metals considered, sodium is the most notable metal that reacts with water at room temperature.

### Final Answer:
The metal which reacts with water at room temperature is **Sodium (Na)**.