Water can be tested by:

Options

A. Smell
B. Taste
C. Hydrated `CuSO_(4)`
D. Anhydrous `CoCl_(2)`(blue) which changes to pink.

Explanation

To test the presence of water, we can use certain chemical substances that change color upon hydration. Here’s a step-by-step solution to the question:

### Step 1: Understanding the Testing Substances
We will use two specific chemicals for testing water:
1. Anhydrous Copper Sulfate (CuSO4)
2. Anhydrous Cobalt(II) Chloride (CoCl2)

### Step 2: Testing with Anhydrous Copper Sulfate
- **Observation**: Anhydrous copper sulfate is white in color.
- **Reaction**: When water is added to anhydrous copper sulfate, it reacts to form hydrated copper sulfate (CuSO4·5H2O).
- **Color Change**: This reaction results in a color change from white to blue.
- **Conclusion**: If the substance turns blue upon the addition of water, we can confirm the presence of water.

### Step 3: Testing with Anhydrous Cobalt(II) Chloride
- **Observation**: Anhydrous cobalt(II) chloride is blue in color.
- **Reaction**: When water is added to anhydrous cobalt(II) chloride, it forms hydrated cobalt(II) chloride (CoCl2·6H2O).
- **Color Change**: This reaction results in a color change from blue to pink.
- **Conclusion**: If the substance turns pink upon the addition of water, we can also confirm the presence of water.

### Step 4: Evaluating Other Testing Methods
- **Smell and Taste**: Testing water by smell and taste is not advisable as it can be dangerous due to potential contamination. Harmful substances may be present that can affect health.
- **Hydrate Form**: The presence of a hydrate form is not a valid test for the presence of water.

### Final Conclusion
The most reliable tests for the presence of water are:
- The use of anhydrous copper sulfate, which turns blue when water is added.
- The use of anhydrous cobalt(II) chloride, which turns pink when water is added.

Thus, the correct answer for testing water is the use of **anhydrous cobalt(II) chloride (CoCl2)**, as it changes color from blue to pink upon the addition of water.

---