From the given following sol how many can coagulate the haemoglobin sol?
`Fe(OH)_(3),Ca(OH)_(2),Al(OH)_(3),` starch, clay, `As_(2)S_(3),CdS,` basic dye.

Options

A. 1
B. 3
C. 4
D. 8

Explanation

To determine how many of the given substances can coagulate the hemoglobin sol, we need to analyze the charge of each substance. Hemoglobin sol is a positively charged colloid, which means it can be coagulated by negatively charged colloids.

### Step-by-Step Solution:

1. **Identify the Charge of Hemoglobin Sol**:
- Hemoglobin sol is positively charged.

2. **List the Given Substances**:
- The substances provided are:
- Fe(OH)₃
- Ca(OH)₂
- Al(OH)₃
- Starch
- Clay
- As₂S₃
- CdS
- Basic dye

3. **Determine the Charge of Each Substance**:
- **Fe(OH)₃**: This is a positively charged colloid due to Fe³⁺ ions.
- **Ca(OH)₂**: This is also a positively charged colloid due to Ca²⁺ ions.
- **Al(OH)₃**: This is a positively charged colloid due to Al³⁺ ions.
- **Starch**: This is a negatively charged colloid.
- **Clay**: This is a negatively charged colloid.
- **As₂S₃**: This is a negatively charged colloid.
- **CdS**: This is a negatively charged colloid.
- **Basic dye**: This is a positively charged colloid.

4. **Identify the Negatively Charged Colloids**:
- From the analysis, the negatively charged colloids are:
- Starch
- Clay
- As₂S₃
- CdS

5. **Count the Negatively Charged Colloids**:
- There are 4 negatively charged colloids that can coagulate the positively charged hemoglobin sol.

### Conclusion:
The total number of substances that can coagulate the hemoglobin sol is **4**.