It is present in rod cells and useful in night vision `,`

Options

A. vitamin K
B. melanin
C. rhodopsin
D. vitamin C

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a substance that is present in rod cells and is useful for night vision.

2. **Analyzing the Options**: The options provided are:
- Vitamin K
- Melanin
- Rhodopsin
- Vitamin C

3. **Evaluating Vitamin K**:
- Vitamin K is known primarily for its role in blood clotting.
- It is a fat-soluble vitamin and is not found in the eyes or specifically in rod cells.
- **Conclusion**: Vitamin K is not the correct answer.

4. **Evaluating Melanin**:
- Melanin is a pigment found in the skin and is responsible for skin color.
- It does not play a role in night vision or is not present in rod cells.
- **Conclusion**: Melanin is not the correct answer.

5. **Evaluating Vitamin C**:
- Vitamin C, also known as ascorbic acid, is a water-soluble vitamin.
- It serves various functions in the body but is not associated with rod cells or night vision.
- **Conclusion**: Vitamin C is not the correct answer.

6. **Evaluating Rhodopsin**:
- Rhodopsin is a photopigment found in rod cells, which are specialized for low-light vision.
- It is a derivative of vitamin A and is crucial for night vision.
- **Conclusion**: Rhodopsin is the correct answer.

7. **Final Answer**: The substance present in rod cells and useful for night vision is **Rhodopsin**.

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