Arthropoda is characterized by

Options

A. Chitinous exoskeleton, segmentation, and jointed appendages
B. Hairs, exoskelaton and three pairs of legs
C. Exocutaneous scales, metamerism , one pair antennae
D. One pair chelicerae, one pair pediplap, and one pair of antennae

Answer

**Step-by-Step Solution:**

1. **Understanding Arthropoda**: Begin by recognizing that Arthropoda is a phylum of invertebrates, which means these organisms do not have a backbone. This is a key characteristic of the group.

2. **Exoskeleton Composition**: The exoskeleton of arthropods is primarily made of chitin. This material provides strength and protection against environmental factors. It is important to note that this is different from a cartilaginous exoskeleton, which is not found in arthropods.

3. **Body Segmentation**: Arthropods exhibit segmentation in their body structure. This means their bodies are divided into distinct segments, which is a common feature in many arthropods.

4. **Jointed Appendages**: One of the most defining features of arthropods is the presence of jointed appendages. This includes legs and other structures that are segmented and allow for a wide range of movement.

5. **Evaluating the Options**: Now, we will evaluate the provided options:
- **Option A**: Cartilaginous exoskeleton, segmentation, and jointed appendages – Incorrect because the exoskeleton is not cartilaginous.
- **Option B**: Hairs, exoskeleton, and three pairs of legs – Incorrect as not all arthropods have three pairs of legs.
- **Option C**: Exocutaneous scales, metamerism, one pair of antenna – Incorrect as arthropods do not have scales.
- **Option D**: One pair of chelicerae, one pair of pedipalps, and one pair of antenna – Incorrect as this description fits specific groups within arthropods, not the entire phylum.

6. **Correct Answer**: The correct answer is **Option A**: chitinous exoskeleton, segmentation, and jointed appendages. This option accurately describes the main characteristics of the phylum Arthropoda.