A rhabditiform larva is formed in the life cycle of

Options

A. Liver fluke
B. Ascaris
C. Tapeworm
D. Planaria

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which organism's life cycle includes the formation of a rhabditiform larva.

2. **Identifying the Options**: The options provided are:
- Liver fluke
- Ascaris
- Tapeworm
- Planaria

3. **Defining Rhabditiform Larva**: Rhabditiform larvae are a specific type of larva that is typically associated with nematodes, particularly Ascaris.

4. **Analyzing Each Option**:
- **Liver Fluke**: The larva associated with liver fluke is called miracidia, not rhabditiform.
- **Ascaris**: Ascaris is a nematode, and it is known to produce rhabditiform larvae during its life cycle.
- **Tapeworm**: The larva associated with tapeworms is called Cysticerus, which is not rhabditiform.
- **Planaria**: Planaria produce a type of larva known as cryptic larva, which is also not rhabditiform.

5. **Conclusion**: The only organism from the options that produces a rhabditiform larva is Ascaris. Therefore, the correct answer is Ascaris.

### Final Answer:
A rhabditiform larva is formed in the life cycle of **Ascaris**.

---