The tympanic cavity, in frog communicates with pharynx ventrally through

Options

A. bidder's canal
B. horizontal canal
C. semicircular canal
D. eustachian tube

Answer

To answer the question regarding how the tympanic cavity in a frog communicates with the pharynx ventrally, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Tympanic Cavity**:
- The tympanic cavity is a part of the frog's ear structure, which plays a role in hearing.

2. **Identifying the Communication Pathway**:
- The question asks how this cavity connects to the pharynx, which is a part of the digestive and respiratory system.

3. **Considering the Options**:
- The options provided include Bidder's canal, horizontal canal, semicircular canal, and Eustachian tube.

4. **Analyzing Each Option**:
- **Bidder's Canal**: This is associated with the kidney and does not connect the tympanic cavity to the pharynx. Therefore, it is incorrect.
- **Horizontal Canal and Semicircular Canal**: These are involved in balance and do not have a role in the communication between the tympanic cavity and the pharynx. Thus, these options are also incorrect.
- **Eustachian Tube**: This is a duct that connects the middle ear (including the tympanic cavity) to the pharynx. It helps in equalizing air pressure in the ear.

5. **Conclusion**:
- The correct answer is that the tympanic cavity in frogs communicates with the pharynx ventrally through the **Eustachian tube**.

### Final Answer:
The tympanic cavity in frogs communicates with the pharynx ventrally through the **Eustachian tube**.