The mature cells of bone are mostly involved in 

Options

A. cell division
B. extra cellular matrix formation
C. regeneration
D. maintaining the matrix

Answer

### Step-by-Step Solution:

1. **Identify the Types of Bone Cells**:
- There are three main types of bone cells: osteoblasts, osteocytes, and osteoclasts.

2. **Understand the Function of Each Cell Type**:
- **Osteoblasts**: These are immature bone cells responsible for the formation of new bone. They eventually mature into osteocytes.
- **Osteocytes**: These are the mature bone cells that arise from osteoblasts. Their primary function is to maintain the bone matrix.
- **Osteoclasts**: These cells are involved in the resorption or destruction of bone tissue.

3. **Focus on the Mature Bone Cells (Osteocytes)**:
- Since the question specifically asks about mature bone cells, we focus on osteocytes.

4. **Determine the Function of Osteocytes**:
- The primary role of osteocytes is to maintain the bone matrix. They help in the regulation of mineral content and ensure the integrity of the bone structure.

5. **Eliminate Incorrect Options**:
- The options related to cell division, extracellular matrix formation, and regeneration do not pertain to the function of mature bone cells (osteocytes).
- Therefore, the correct answer is that mature bone cells are mostly involved in maintaining the matrix.

### Final Answer:
The mature cells of bone (osteocytes) are mostly involved in **maintaining the matrix**.

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