The matrix of bone is hard due to ...A ... while that of cartilage is pliable due to ....B …….

Options

A. `{:(A,B),("Calcium salts","Chondroitin salts"):}`
B. `{:(A,B),("Calcium salts","Hyaluronic acid A "):}`
C. `{:(A,B),("Chondroitin Sulphate","Hyaluronic acid "):}`
D. `{:(A,B),("Chondroitin Sulphate","Calcium salts"):}`

Answer

To answer the question, we need to fill in the blanks regarding the properties of the matrix of bone and cartilage.

### Step-by-Step Solution:

1. **Understanding Bone Matrix:**
- The matrix of bone is known for its hardness. This hardness is primarily due to the presence of certain minerals.
- The main component responsible for the hardness of bone is **calcium salts**. These minerals provide strength and rigidity to the bone structure.

2. **Understanding Cartilage Matrix:**
- In contrast, the matrix of cartilage is known for its pliability and flexibility. This is crucial for its function in various parts of the body, such as the joints, nose, and ears.
- The pliability of cartilage is primarily due to the presence of **chondroitin sulfate** and other components like collagen fibers. These substances allow cartilage to be flexible and resilient.

3. **Filling in the Blanks:**
- Therefore, we can fill in the blanks as follows:
- A: **calcium salts**
- B: **chondroitin sulfate**

### Final Answer:
The matrix of bone is hard due to **calcium salts** while that of cartilage is pliable due to **chondroitin sulfate**.