The total number of segments of cockroach with continuous segmental ganglia are

Options

A. 5
B. 7
C. 8
D. 6

Answer

To determine the total number of segments of a cockroach that have continuous segmental ganglia, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Body Segments of the Cockroach**:
- The cockroach's body is divided into three main regions: the head, thorax, and abdomen.
- The thorax consists of 3 segments, and the abdomen consists of 10 segments.

2. **Understand the Nervous System Structure**:
- The nervous system of the cockroach is made up of segmental ganglia, which are clusters of nerve cells.
- Ganglia are present in both the thorax and abdomen regions.

3. **Count the Ganglia in the Thorax**:
- All three segments of the thorax (1st, 2nd, and 3rd) have ganglia.

4. **Count the Ganglia in the Abdomen**:
- In the abdomen, ganglia are present in the 1st, 2nd, 3rd, 4th, 6th, and 7th segments.
- The 5th, 8th, 9th, and 10th segments do not have ganglia.

5. **Determine the Total Number of Segments with Ganglia**:
- The total segments with ganglia in the thorax = 3 (from the thorax).
- The total segments with ganglia in the abdomen = 4 (1st, 2nd, 3rd, 4th).
- The 6th and 7th segments also have ganglia, adding 2 more to the count.

6. **Identify Continuous Segments**:
- The segments with continuous ganglia start from the 1st thoracic segment and continue through the 4th abdominal segment.
- Therefore, the continuous segments with ganglia are: 1st thorax, 2nd thorax, 3rd thorax, 1st abdomen, 2nd abdomen, 3rd abdomen, and 4th abdomen.

7. **Final Count**:
- Adding these together gives us a total of 7 segments with continuous segmental ganglia.

### Conclusion:
The total number of segments of the cockroach with continuous segmental ganglia is **7**.

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