In Hydra, egestion of undigested food and excretion of nitrogenous wastes occur through

Options

A. Mouth and mouth
B. Body wall and body wall
C. Mouth and body wall
D. Mouth and tentacles.

Answer

### Step-by-Step Solution:

1. **Understanding Hydra's Anatomy**: Hydra is a simple organism belonging to the phylum Cnidaria, also known as Coelenterata. It has a tubular body with a mouth at one end, surrounded by tentacles.

2. **Identifying Functions**: In Hydra, two main processes need to be considered: egestion of undigested food and excretion of nitrogenous wastes.

3. **Egestion Process**: Egestion refers to the removal of undigested food. In Hydra, this process occurs through the mouth. When food is ingested and not digested, it is expelled back through the mouth.

4. **Excretion Process**: Excretion in Hydra involves the removal of nitrogenous wastes, primarily in the form of ammonia. Hydra does not have specialized organs for excretion; instead, nitrogenous wastes diffuse through the general body surface (the body wall).

5. **Combining the Processes**: Since egestion occurs through the mouth and excretion occurs through the body wall, we can conclude that the correct answer involves both structures.

6. **Choosing the Correct Option**: Among the provided options:
- Mouth and mouth: Incorrect (only egestion)
- Body wall and body wall: Incorrect (only excretion)
- Mouth and body wall: Correct (egestion through mouth, excretion through body wall)
- Mouth and tentacles: Incorrect (tentacles are primarily for capturing prey)

Thus, the correct answer is **Mouth and Body Wall**.