Mode of respiration in mollusca is :
A. Buccal respiration
B. Bronchial
C. Pulmonary

Question

Accepted Answer

The mode of respiration in mollusca is primarily bronchial and, in some cases, pulmonary, which aligns with Option 3: "Only B and C."

1. **Explanation for Option 3 (Correct Answer):**
   - **Bronchial Respiration (B):** Most mollusks, especially aquatic ones like bivalves and gastropods, use gills for respiration. These gills are specialized structures that facilitate gas exchange in water, making bronchial respiration a common mode in mollusca.
   - **Pulmonary Respiration (C):** Some mollusks, particularly terrestrial gastropods like land snails, have adapted to life on land and possess a lung-like structure for breathing air. This adaptation allows for pulmonary respiration, which is why Option C is also correct.

2. **Explanation for why other options are incorrect:**
   - **Option 1 (Only A and C):** Buccal respiration (A) is not a mode of respiration in mollusca. Buccal respiration typically refers to a method of breathing involving the mouth, seen in some amphibians, but not in mollusks. Therefore, including A makes this option incorrect.
   - **Option 2 (Only B and A):** As mentioned, buccal respiration (A) is not applicable to mollusca. While bronchial respiration (B) is correct, the inclusion of A makes this option incorrect.
   - **Option 4 (A, B, and C):** This option includes buccal respiration (A), which is not a mode of respiration in mollusca. Therefore, this option is incorrect due to the inclusion of A.

In summary, Option 3 is correct because it accurately identifies the modes of respiration in mollusca as bronchial and pulmonary, without including buccal respiration, which is not applicable to this phylum.