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 solve the question regarding the characteristics of Obelia, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Obelia**:
- Obelia is a genus that belongs to the phylum Cnidaria. Members of this phylum typically exhibit two body forms: the polyp and the medusa.

2. **Analyzing Option A**:
- **Ciliated free swimming planula larva**:
- In Cnidarians, the planula larva is indeed ciliated and free-swimming. This statement is **correct**.

3. **Analyzing Option B**:
- **Metagenesis**:
- Metagenesis refers to the alternation of generations, which is a characteristic of many Cnidarians, including Obelia. This statement is also **correct**.

4. **Analyzing Option C**:
- **Acraspedote medusa**:
- Acraspedote medusae lack a velum (a membrane that helps in swimming). Obelia does not have an acraspedote medusa; it has a craspedote medusa. Therefore, this statement is **incorrect**.

5. **Analyzing Option D**:
- **Statocysts present in medusoid stage**:
- Statocysts are balance sensory organs that are present in the medusa stage of Cnidarians, including Obelia. This statement is **correct**.

### Conclusion:
Based on the analysis:
- The correct characteristics of Obelia are A (Ciliated free swimming planula larva), B (Metagenesis), and D (Statocysts present in medusoid stage).
- The incorrect characteristic is C (Acraspedote medusa).

Thus, the answer to the question is **A, B, and D are characteristics of Obelia**.