Indirect development (larval stages) is found in

Options

A. Mollusca
B. Echinodermata
C. Hemichordata
D. All of the above

Answer

To solve the question regarding which groups exhibit indirect development with larval stages, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Indirect Development**:
- Indirect development refers to a developmental process where an organism goes through one or more larval stages before reaching adulthood. During this process, the larva is often morphologically and functionally different from the adult form.

2. **Identifying the Groups**:
- We need to analyze the given options to see which of these groups are known for having indirect development:
- **Option 1: Molluscs**: Many molluscs, such as bivalves and gastropods, have a larval stage called trochophore or veliger.
- **Option 2: Echinodermata**: Echinoderms, like sea stars and sea urchins, also have a larval stage (e.g., bipinnaria) that is quite different from the adult form.
- **Option 3: Hemichordata**: Hemichordates, such as acorn worms, have a larval stage known as the tornaria larva.
- **Option 4: All of the above**: This option suggests that all the mentioned groups exhibit indirect development.

3. **Conclusion**:
- Since all three groups (Molluscs, Echinodermata, and Hemichordata) are known to have larval stages in their life cycles, the correct answer is **Option 4: All of the above**.

### Final Answer:
The correct option is **Option 4: All of the above**.