Assertion: In Periplaneta, only superposition or overlappmg images are formed.
Reason: Retinal pigment sheath remains contracted throughout the life.

Options

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

Answer

To analyze the assertion and reason provided in the question, we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that in Periplaneta (the cockroach), only superposition or overlapping images are formed.
- Cockroaches have compound eyes, which are made up of multiple units called ommatidia.

2. **Function of Ommatidia**:
- Each ommatidium can capture light and form an image. In nocturnal insects like cockroaches, the ommatidia do not separate the images they form.
- This leads to the formation of superposition images, where multiple images overlap to create a single image.

3. **Understanding the Reason**:
- The reason given is that the retinal pigment sheath remains contracted throughout the life of the cockroach.
- The retinal pigment sheath is a layer that typically separates the ommatidia in some insects, allowing for distinct images to be formed.

4. **Evaluating the Reason**:
- In cockroaches, the retinal pigment sheath is not present or is contracted, which means that the ommatidia can receive light without separation.
- This absence of separation allows for the formation of superposition images, confirming the assertion.

5. **Conclusion**:
- The assertion is true because cockroaches do form superposition images due to the structure of their compound eyes.
- The reason is misleading because it implies that the retinal pigment sheath's contraction is the cause of superposition images, whereas it is actually the absence of separation that allows for this phenomenon. Thus, the reason is false.

### Final Evaluation:
- The assertion is true, and the reason is false. Therefore, the correct answer is that the assertion is true, and the reason is false.