Basic unit in the eye of cockroach/insect is

Options

A. Retina
B. Rhabdome
C. Corneal facet
D. Ommatidium.

Explanation

To answer the question regarding the basic unit in the eye of a cockroach/insect, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Eye Structure**: The eyes of insects, including cockroaches, are typically compound eyes, which are different from the simple eyes found in some other organisms.

2. **Identifying the Components**: The compound eyes of arthropods are made up of numerous small units. Each of these units has a specific name.

3. **Exploring the Options**:
- **Retina**: This is a part of the eye that contains photoreceptor cells, but it is not the basic unit in the compound eyes of insects.
- **Reptile**: This option is irrelevant as it refers to a different class of animals and not to the structure of insect eyes.
- **Corneal Facet**: These are the small, flat surfaces on the compound eye but do not represent the basic functional unit.
- **Ommatidium**: This is the correct term for the basic unit of the compound eye in insects. Each ommatidium consists of a cluster of photoreceptor cells surrounded by supporting cells and pigment cells.

4. **Conclusion**: Based on the analysis of the options, the basic unit in the eye of a cockroach/insect is the **ommatidium**.

### Final Answer:
The basic unit in the eye of a cockroach/insect is **ommatidium**.

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