Characteristics of class Crustacea are

Options

A. Cephalothorax, biramous appendages, and gills
B. Head and thorax, book lungs, and chitinous exoskeleton
C. Cephalothorax, book lungs and chitinous exoskeleton
D. Head and thorax, biramous appendages, and book lungs

Answer

### Step-by-Step Solution for the Characteristics of Class Crustacea

1. **Introduction to Crustacea**:
- Crustacea is a class within the phylum Arthropoda. This class includes a variety of aquatic animals such as crabs, lobsters, and shrimps.

**Hint**: Remember that Crustacea is part of the larger phylum Arthropoda.

2. **Body Structure**:
- Crustaceans typically have a body that is segmented. The head (cephalon) and thorax may be fused to form a structure known as the cephalothorax.

**Hint**: Focus on the fusion of head and thorax as a key characteristic.

3. **Appendages**:
- They possess biramous appendages, meaning that each appendage is divided into two branches. This is a distinctive feature of crustaceans.

**Hint**: "Biramous" means "two branches" – think about how their limbs are structured.

4. **Respiration**:
- Most crustaceans respire through gills, which are usually located at the base of their legs where they attach to the thorax. This adaptation is essential for their aquatic lifestyle.

**Hint**: Gills are crucial for breathing in water – remember where they are located.

5. **Exoskeleton**:
- Crustaceans have a chitinous exoskeleton, which provides protection and support. This exoskeleton is often hardened and can be quite robust.

**Hint**: Chitin is a common material in the exoskeletons of many arthropods.

6. **Conclusion**:
- The main characteristics of class Crustacea include:
- Cephalothorax (fusion of head and thorax)
- Biramous appendages
- Gills for respiration
- Chitinous exoskeleton

**Hint**: Summarize the key features to reinforce your understanding.

### Final Answer
The characteristics of class Crustacea are:
- Cephalothorax
- Biramous appendages
- Gills for respiration
- Chitinous exoskeleton