Which of the following is correct for the circulatory system of cockroach?

Options

A. It is present on the dorsal side and it has thirteen units of heart in abdominal region
B. It is present on the ventral side and it has ten abdominal and three thoracic units of heart
C. It is present on the ventral side and it has thirteen units of heart in abdominal region
D. It is present on the dorsal side and it has ten abdominal and three thoracic units of heart

Answer

To solve the question about the circulatory system of a cockroach, we need to analyze each of the provided options carefully.

### Step-by-Step Solution:

1. **Understanding the Circulatory System of Cockroach**:
- The circulatory system of cockroaches is an open type of circulatory system. This means that blood is not always contained within blood vessels but flows freely through cavities.

2. **Identifying the Location of the Heart**:
- The heart of a cockroach is located on the dorsal side (the back side) of its body. This is a key point to remember when evaluating the options.

3. **Counting the Heart Units**:
- The cockroach has a total of 13 heart chambers. These are divided into:
- 10 abdominal heart chambers
- 3 thoracic heart chambers

4. **Evaluating Each Option**:
- **Option 1**: "It is present on the dorsal side and it has 13 units of heart in abdominal region."
- This is incorrect because while it is on the dorsal side, it does not have all 13 units in the abdominal region; it has 10 abdominal and 3 thoracic.

- **Option 2**: "It is present on the ventral side and it has 10 abdominal and 3 thoracic units of heart."
- This is incorrect because the circulatory system is on the dorsal side, not the ventral side.

- **Option 3**: "It is present on the ventral side and it has 13 units of heart in abdominal region."
- This is incorrect for the same reasons as option 2; it is on the dorsal side and not all units are in the abdominal region.

- **Option 4**: "It is present on the dorsal side and it has 10 abdominal and 3 thoracic units of heart."
- This is correct as it accurately describes the location and the number of heart units.

5. **Conclusion**:
- The correct answer is **Option 4**: "It is present on the dorsal side and it has 10 abdominal and 3 thoracic units of heart."