Assertion : Yellow spot is the area of most distinct day vision.
Reason : Yellow spot is with only cone cells.

Options

A. If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
C. If Assertion is true but Reason is false.
D. If both Assertion and Reason are false.

Answer

To solve the question regarding the assertion and reason about the yellow spot in the human eye, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Yellow spot is the area of most distinct day vision."
- This is true because the yellow spot, also known as the fovea centralis or macula lutea, is located at the center of the retina and is responsible for sharp, detailed vision during daylight.

**Hint**: Recall the function of the yellow spot in the retina.

2. **Understanding the Reason**:
- The reason states that "Yellow spot is with only cone cells."
- This is also true. The yellow spot contains a high concentration of cone cells, which are photoreceptors responsible for color vision and function best in bright light.

**Hint**: Consider the types of photoreceptor cells in the retina and their functions.

3. **Analyzing the Relationship**:
- Since both the assertion and the reason are true, we need to determine if the reason correctly explains the assertion.
- The presence of cone cells in the yellow spot directly contributes to its role in providing distinct vision during the day.

**Hint**: Think about how the structure of the yellow spot supports its function.

4. **Conclusion**:
- Both the assertion and the reason are true, and the reason is the correct explanation of the assertion. Therefore, the correct answer is that both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

**Hint**: Look for options that confirm both statements are true and that one explains the other.

### Final Answer:
Both assertion and reason are true, and the reason is the correct explanation of the assertion.