The ducts in male reproductive system of earthworm that open exterior through pores in `18^(th)` segment are  

Options

A. a. common prostatic & oviducts
B. b. ducts of accesory glands & prostatic ducts
C. c. oviducts & prostatic ducts
D. d. common prostatic duct & spermatic ducts

Answer

To solve the question regarding the ducts in the male reproductive system of earthworms that open to the exterior through pores in the 18th segment, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Earthworm's Reproductive System**: Recognize that earthworms are hermaphrodites, meaning they possess both male and female reproductive organs in the same individual.

2. **Identify Male Reproductive Structures**: Focus on the male reproductive structures, which include:
- **Testes**: Located in the 10th and 11th segments.
- **Seminal Vesicles**: Found in the 11th and 12th segments.
- **Vas deferens**: A long tube that runs from the testes and connects to the 18th segment.

3. **Locate the Ducts**: The ducts that open to the exterior through the 18th segment are specifically:
- **Common Prostate Duct**
- **Spermatic Duct**

4. **Conclusion**: The ducts that open to the exterior through pores in the 18th segment of the earthworm are the common prostate duct and the spermatic duct.

5. **Final Answer**: Therefore, the correct answer to the question is that the ducts in the male reproductive system of earthworm that open exterior through pores in the 18th segment are the **Common Prostate Duct and Spermatic Duct**.