Which one of the following are not included in the phylum Mollusca ?

Options

A. Clams
B. Squids
C. Lobsters
D. Snails

Explanation

To determine which of the given options is not included in the phylum Mollusca, we can analyze each option provided:

1. **Clams**: Clams are bivalve mollusks, which means they have a two-part hinged shell. They are definitely included in the phylum Mollusca.

2. **Squids**: Squids are cephalopods, another class within the phylum Mollusca. They are also included in this phylum.

3. **Lobsters**: Lobsters are not mollusks; they belong to the phylum Arthropoda, specifically the class Crustacea. They have jointed legs and a hard exoskeleton, which are characteristics of crustaceans, not mollusks.

4. **Snails**: Snails are gastropods and are included in the phylum Mollusca. They have a single, often spirally coiled shell.

Based on this analysis, the correct answer to the question is **Lobsters**, as they are not included in the phylum Mollusca.

### Step-by-Step Solution:
1. **Identify the options**: Clams, Squids, Lobsters, Snails.
2. **Analyze each option**:
- Clams: Belong to Mollusca.
- Squids: Belong to Mollusca.
- Lobsters: Belong to Arthropoda (Crustacea).
- Snails: Belong to Mollusca.
3. **Determine which is not part of Mollusca**: Lobsters are the only option that does not belong to the phylum Mollusca.
4. **Conclude the answer**: The answer is Lobsters.