The parasite which completes its life cycle in a single host is

Options

A. (a) Fasciole hepatica
B. (b) Plasmodium vivax
C. (c) Taehia solium
D. (d) Ascaris lumbricoides

Answer

To solve the question regarding which parasite completes its life cycle in a single host, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding the Question**: We need to identify a parasite that completes its entire life cycle within a single host.

2. **Analyzing the First Option - Fasciola**:
- Commonly known as the liver fluke.
- Causes the disease called Fascioliasis.
- This parasite has two hosts: snails and sheep.
- **Conclusion**: Fasciola does not complete its life cycle in a single host.

3. **Analyzing the Second Option - Plasmodium**:
- Known for causing malaria.
- It requires two hosts: humans and mosquitoes.
- **Conclusion**: Plasmodium does not complete its life cycle in a single host.

4. **Analyzing the Third Option - Taenia**:
- A type of flatworm that causes Taeniasis.
- It has two hosts: pigs and humans.
- **Conclusion**: Taenia does not complete its life cycle in a single host.

5. **Analyzing the Fourth Option - Ascaris**:
- Known as roundworms and causes Ascariasis.
- This parasite completes its life cycle in a single host, which is humans.
- It can transmit from human to human or via soil.
- **Conclusion**: Ascaris is the correct answer as it completes its life cycle in a single host.

### Final Answer:
The parasite which completes its life cycle in a single host is **Ascaris**.

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