Apis, Bombyx , Culex and Limulus belongs to

Options

A. the largest phylum of animalia
B. the smallest group of animalia
C. the second-largest animal phylum
D. the animals have an endoskeleton of calcareous ossicles

Answer

### Step-by-Step Solution:

1. **Identify the Organisms**: The organisms mentioned in the question are Apis, Bombyx, Culex, and Limulus.

2. **Determine the Classification**: To classify these organisms, we need to look at their common characteristics.

3. **Analyze Characteristics**:
- **Segmented Body**: All these organisms have a segmented body structure.
- **Body Regions**: They possess distinct body regions, including a head, thorax, and abdomen.
- **Jointed Appendages**: They have jointed appendages, which is a key feature of arthropods.
- **Nervous System**: They possess a nervous system.
- **Exoskeleton**: They have a protective exoskeleton made of chitin, which provides physical protection and prevents desiccation.

4. **Phylum Identification**: Based on the characteristics mentioned above, all these organisms belong to the phylum **Arthropoda**.

5. **Largest Phylum**: Arthropoda is known as the largest phylum in the animal kingdom, containing the maximum number of species.

6. **Eliminate Other Options**:
- The smallest group of Animalia is incorrect as they belong to the largest.
- Mollusca is the second-largest phylum and includes shelled organisms, which does not apply here.
- The mention of an endoskeleton of calcareous ossicles refers to echinoderms, which is also incorrect.

7. **Conclusion**: Therefore, the correct answer is that Apis, Bombyx, Culex, and Limulus belong to the phylum **Arthropoda**.