The method used to remove temporary hardness of water is:

Options

A. Synthetic resins method
B. Calgon's method
C. Clark's method
D. Ion-exchange method

Explanation

To solve the question regarding the method used to remove temporary hardness of water, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hardness of Water**:
- Water can be classified as soft or hard based on its ability to form lather with soap. Hard water does not form lather easily due to the presence of certain salts.

2. **Types of Hardness**:
- There are two types of hardness: **temporary hardness** and **permanent hardness**.
- **Temporary hardness** is primarily caused by the presence of bicarbonates of calcium (Ca(HCO₃)₂) and magnesium (Mg(HCO₃)₂) in water.
- **Permanent hardness** is caused by the presence of chlorides and sulfates of calcium and magnesium.

3. **Identifying the Method to Remove Temporary Hardness**:
- To remove temporary hardness, we need a method that can convert bicarbonates into insoluble carbonates.
- The most common method used for this purpose is **Clark's method**.

4. **Clark's Method**:
- In Clark's method, a small amount of calcium hydroxide (slaked lime, Ca(OH)₂) is added to the hard water.
- The reaction that occurs is:
\[ \text{Ca(OH)}_2 + \text{Ca(HCO}_3\text{)}_2 \rightarrow 2 \text{CaCO}_3 \downarrow + 2 \text{H}_2\text{O} \]
\[ \text{Ca(OH)}_2 + \text{Mg(HCO}_3\text{)}_2 \rightarrow \text{MgCO}_3 \downarrow + \text{CaCO}_3 \downarrow + 2 \text{H}_2\text{O} \]
- The calcium and magnesium bicarbonates are converted into insoluble calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃), which precipitate out of the solution.

5. **Filtration**:
- The precipitated carbonates can then be easily removed by filtration, thus effectively reducing the temporary hardness of the water.

### Conclusion:
The method used to remove temporary hardness of water is **Clark's method**.

---