Arrange the number of species of phylum Arthropoda ( (A)) , phylum Chordata ((B),) and phylum Mollusca ((C)) in ascending order.

Options

A. `B lt C ltA`
B. `B lt A lt C`
C. C = B lt A
D. C lt B lt A

Answer

To arrange the number of species of the phylum Arthropoda (A), phylum Chordata (B), and phylum Mollusca (C) in ascending order, we need to first understand the number of species present in each phylum.

### Step-by-Step Solution:

1. **Identify the Phyla**:
- Phylum Arthropoda (A)
- Phylum Chordata (B)
- Phylum Mollusca (C)

2. **Determine the Number of Species**:
- **Phylum Arthropoda**: This is known to be the largest phylum in the animal kingdom, with approximately 1 million described species and possibly many more undiscovered.
- **Phylum Mollusca**: This is the second largest phylum, with around 85,000 described species.
- **Phylum Chordata**: This phylum has the fewest species compared to the other two, with about 65,000 described species.

3. **Arrange in Ascending Order**:
- Based on the number of species:
- Phylum Chordata (B) - 65,000 species
- Phylum Mollusca (C) - 85,000 species
- Phylum Arthropoda (A) - 1,000,000 species

4. **Final Arrangement**:
- The ascending order of the number of species is:
- B (Chordata) < C (Mollusca) < A (Arthropoda)

### Final Answer:
**B < C < A**