Visual units of compound eyes of cockroach are taenidia/ommatidia.

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the visual units of the compound eyes of cockroaches. We need to identify the correct term that describes these units.

2. **Identifying the Visual Units**: The visual units of the compound eyes in cockroaches are called **ommatidia**. Each ommatidium is a small, individual visual receptor that contributes to the overall image perceived by the cockroach.

3. **Explaining Ommatidia**: Each compound eye of a cockroach consists of approximately 2000 ommatidia. These structures are responsible for forming images that are magnified, allowing cockroaches to see their surroundings clearly.

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