The chemical used as a fixer/developer in photography is

Options

A. sodium sulphate
B. sodium sulphide
C. sodium thiosulphate
D. sodium bicarbonate

Explanation

To solve the question regarding the chemical used as a fixer/developer in photography, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Role of Fixer/Developer**: In photography, a fixer is a chemical used to remove unexposed silver halides from the photographic film or paper. This process makes the image permanent and prevents further exposure to light.

2. **Identifying the Chemicals**: We have four options to consider:
- Sodium Sulphate
- Sodium Sulphide
- Sodium Thiosulphate
- Sodium Bicarbonate

3. **Analyzing Each Option**:
- **Sodium Sulphate (Na2SO4)**: Primarily used in detergents and glass manufacturing, not as a fixer.
- **Sodium Sulphide (Na2S)**: Used in various industrial processes, but not in photography.
- **Sodium Thiosulphate (Na2S2O3)**: Commonly known as hypo, it is widely used in photography as a fixer.
- **Sodium Bicarbonate (NaHCO3)**: Commonly known as baking soda, it is not used as a fixer in photography.

4. **Conclusion**: The correct answer is **Sodium Thiosulphate**, which is used as a fixer in photography to develop images.

### Final Answer:
The chemical used as a fixer/developer in photography is **Sodium Thiosulphate** (Na2S2O3).

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