If an earthworm has 100 segments, total number of segments with two types of nephridia are 

Options

A. 80
B. 70
C. 89
D. 86

Answer

To solve the question regarding the total number of segments in an earthworm that contain two types of nephridia, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Types of Nephridia**:
- The three types of nephridia in earthworms are:
- Intersegmental nephridia
- Pharyngeal nephridia
- Septal nephridia

2. **Determine the Segments for Each Type**:
- **Intersegmental Nephridia**: Present from the 3rd segment to the 100th segment.
- **Pharyngeal Nephridia**: Present in the 4th, 5th, and 6th segments.
- **Septal Nephridia**: Present from the 15th segment to the 100th segment.

3. **Count Segments with Intersegmental Nephridia**:
- Intersegmental nephridia are present from segments 3 to 100, which gives us:
- Total segments = 100 - 3 + 1 = 98 segments.

4. **Count Segments with Pharyngeal Nephridia**:
- Pharyngeal nephridia are present in segments 4, 5, and 6, which gives us:
- Total segments = 3 segments.

5. **Count Segments with Septal Nephridia**:
- Septal nephridia are present from segments 15 to 100, which gives us:
- Total segments = 100 - 15 + 1 = 86 segments.

6. **Calculate Total Segments with Two Types of Nephridia**:
- **Intersegmental and Pharyngeal**: Segments 4, 5, and 6 are counted in both types. So, we have:
- Total segments with both = 3 (from pharyngeal) + (86 segments from septal starting from 15 to 100) = 89 segments.

### Final Answer:
The total number of segments with two types of nephridia is **89**.