Sites of first, second and third moulting of Ascaris larva are

Options

A. soil, lung, intestine
B. soil, alveoli, lung
C. soil, intestine, lung
D. liver, stomach, intestine

Answer

### Step-by-Step Solution:

1. **Understanding Moulting**: Moulting is the process where an organism sheds its outer layer and replaces it. This is common in various life stages of many organisms, including Ascaris larvae.

2. **Identifying Ascaris**: Ascaris is a type of nematode, commonly known as a roundworm, which primarily inhabits the small intestine of its host.

3. **First Moulting**: The first moulting of the Ascaris larva occurs in the soil. After fertilization, the eggs are excreted with the feces of the host and enter the soil, where the first larval stage develops and undergoes its first moult.

4. **Second Moulting**: The second moulting occurs when the larva is ingested by a host. This can happen through contaminated food or water. Once inside the host, the larva undergoes its second moult.

5. **Third Moulting**: The third moulting takes place in the lungs. After the second stage larva hatches into a juvenile, it enters the circulatory system of the host, travels to the heart, and then moves to the lungs. The alveoli in the lungs serve as the site for the third moult.

6. **Summary of Sites**:
- **First Moulting**: Soil
- **Second Moulting**: Intestine (inside the host)
- **Third Moulting**: Lungs (specifically in the alveoli)

### Final Answer:
- The sites of the first, second, and third moulting of Ascaris larva are:
1. First Moulting: Soil
2. Second Moulting: Intestine
3. Third Moulting: Lungs

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