The sequence of passage of air into lungs in frog is 

Options

A. external nostrils - buccopharyngeal cavity - glottis - lungs
B. internal nostrils - pharynx - lungs - glottis
C. external nostirls - buccopharyngeal cavity - lungs - internal nostrils
D. all the above

Answer

To answer the question about the sequence of passage of air into the lungs in frogs, we can break down the process step by step:

### Step-by-Step Solution:

1. **External Nostrils**: The process begins with the air entering through the external nostrils. These are the anterior openings on the frog's head that allow air to enter the respiratory system.

**Hint**: Think of the external nostrils as the first gateway for air into the frog's body.

2. **Buccopharyngeal Cavity**: After passing through the external nostrils, the air moves into the buccopharyngeal cavity. This cavity expands and contracts to help draw air in.

**Hint**: Remember that the buccopharyngeal cavity acts like a balloon, expanding to take in air.

3. **Glottis**: The next step involves the air moving through the glottis, which is a slit-like opening located in the pharynx. The glottis controls the airflow and ensures that air moves into the lungs.

**Hint**: Visualize the glottis as a valve that opens and closes to regulate air passage.

4. **Lungs**: Finally, the air enters the lungs, where gas exchange occurs. Frogs can also exchange gases through their skin, but the primary function of the lungs is to facilitate this exchange.

**Hint**: Think of the lungs as the main site for oxygen absorption and carbon dioxide release.

### Final Sequence:
Thus, the correct sequence of air passage in frogs is:
1. External Nostrils
2. Buccopharyngeal Cavity
3. Glottis
4. Lungs

### Conclusion:
The correct answer to the question is option A: External Nostrils → Buccopharyngeal Cavity → Glottis → Lungs.