Obelia is characterised by
A. Ciliated free swimming planula larva
B. Metagenesis ltBrgt C. Acraspedote medusa
D. statocysts present in medusoid stage

Options

A. A & B
B. B only
C. A, B & D
D. A, B, C & D

Explanation

To determine the correct characterization of Obelia from the given options, we need to analyze each option based on our knowledge of the organism and its life cycle.

### Step-by-Step Solution:

1. **Understanding Obelia**:
- Obelia is a colonial organism belonging to the phylum Cnidaria. It exhibits two body forms in its life cycle: the polyp form and the medusa form.

2. **Analyzing Option A**:
- **Ciliated free swimming planula larva**:
- In Cnidarians, the larval stage is known as the planula, which is indeed ciliated and free-swimming. This option is **correct**.

3. **Analyzing Option B**:
- **Metagenesis**:
- Metagenesis refers to the alternation of generations, where an organism alternates between asexual (polyp) and sexual (medusa) reproduction. Obelia exhibits this characteristic, making this option **correct**.

4. **Analyzing Option C**:
- **Acraspedote medusa**:
- Acraspedote medusae lack a velum, which is a membrane that helps in swimming. However, in Obelia, the medusa is not classified as acraspedote, as it has a velum and is capable of sexual reproduction. Therefore, this option is **incorrect**.

5. **Analyzing Option D**:
- **Statocysts present in medusoid stage**:
- Statocysts are sensory organs that help maintain balance and orientation in free-swimming organisms. In the medusa stage of Obelia, statocysts are indeed present, making this option **correct**.

### Conclusion:
Based on the analysis:
- Option A is correct.
- Option B is correct.
- Option C is incorrect.
- Option D is correct.

Thus, the correct characteristics of Obelia are A, B, and D.

### Final Answer:
**A, B, and D are correct. C is incorrect.**

---