To test whether a given clear liquid is water, of the following methods, the best one could be

Options

A. Smell the liquids
B. Add anhydrous copper sulphate and look for a colour change
C. Taste the liquid
D. Moisten litmus paper with the solution.

Answer

To determine whether a given clear liquid is water, we can evaluate the four proposed methods:

1. **Smell the liquid**: Pure water is odorless. Therefore, this method is not effective because if the liquid has no smell, we cannot conclude it is water.

2. **Add anhydrous copper sulfate**: Anhydrous copper sulfate (CuSO₄) is a white solid that turns blue when it absorbs water and becomes hydrated copper sulfate (CuSO₄·5H₂O). If we add the clear liquid to anhydrous copper sulfate and it turns blue, this indicates the presence of water in the liquid.

3. **Taste the liquid**: Pure water is tasteless. Therefore, tasting the liquid would not help us identify it as water, as it may not provide any distinguishing flavor.

4. **Moisten litmus paper with the solution**: Water is neutral with a pH of 7, which means it does not change the color of litmus paper. Thus, this method would not provide conclusive evidence that the liquid is water.

After evaluating all four methods, the best method to test whether the clear liquid is water is to **add anhydrous copper sulfate**. If the liquid turns the anhydrous copper sulfate from white to blue, it confirms that the liquid is indeed water.

### Final Answer:
The best method to test whether the given clear liquid is water is to **add anhydrous copper sulfate**.