Trochophore larve occurs in

Options

A. Annelida and Porifera
B. Coelenterata and Annelida
C. Mollusca and Coelenterata
D. Annelida and Mollusca

Answer

To solve the question regarding the occurrence of trochophore larvae, we will follow these steps:

### Step 1: Understand the Definition of Trochophore Larvae
Trochophore larvae are small, free-swimming larvae that are characterized by their spherical or pear shape and are covered by a ring of cilia known as the prototroch. These cilia aid in swimming.

**Hint:** Remember that trochophore larvae are defined by their shape and the presence of cilia.

### Step 2: Identify the Phyla Mentioned
The question lists four options:
1. Annelida and Porifera
2. Cnidaria (previously referred to as Silentrata) and Annelida
3. Mollusca and Cnidaria
4. Annelida and Mollusca

**Hint:** Focus on the specific phyla mentioned in the options.

### Step 3: Analyze Each Phylum for Trochophore Larvae
- **Annelida:** This phylum is known to have trochophore larvae.
- **Porifera:** The larval stage here is known as Parenchymula, not trochophore.
- **Cnidaria (Silentrata):** The larval stage is called planula, not trochophore.
- **Mollusca:** This phylum also has trochophore larvae.

**Hint:** Compare the larval stages of each phylum to determine which contain trochophore larvae.

### Step 4: Determine the Correct Answer
From the analysis:
- Annelida has trochophore larvae.
- Mollusca has trochophore larvae.
- Porifera and Cnidaria do not have trochophore larvae.

Thus, the correct answer is **Annelida and Mollusca**.

**Hint:** Look for the phyla that are known to have trochophore larvae to find the right answer.

### Final Answer
Trochophore larvae occur in **Annelida and Mollusca**.