The female genital pore opens on the 

Options

A. `9^(th)` sternum
B. `10^(th)` sternum
C. `8^(th)` sternum
D. `11^(th)` sternum

Answer

To answer the question "The female genital pore opens on the," we need to analyze the anatomy of the cockroach, specifically focusing on the sternum and the segments of the abdomen.

### Step-by-Step Solution:

1. **Identify the Organism**: The question pertains to the cockroach, scientifically known as Periplaneta americana, which belongs to the phylum Arthropoda.

2. **Understand the Body Structure**: The cockroach's body is divided into three main parts: the head, thorax, and abdomen. The abdomen consists of 10 segments.

3. **Examine the Abdomen Segments**: Among these 10 abdominal segments, the 7th, 8th, and 9th segments are particularly important as they form the brood or genital part of the cockroach.

4. **Locate the Female Genital Pore**: The female genital pore is specifically located on the 8th sternum. The 8th sternum contains a pair of structures known as gonopophysis, which serve as the genital aperture.

5. **Clarify the Other Options**:
- The 9th sternum does not contain the female genital pore; instead, it has the gonophore and spermatical pores.
- The 10th sternum is not relevant for the female genital pore.
- There is no 11th sternum in the cockroach.

6. **Conclusion**: Therefore, the female genital pore opens on the **8th sternum**.

### Final Answer:
The female genital pore opens on the **8th sternum**.