The character associated with cartilage 

Options

A. Reactivation of pre-existing chondrocytes
B. Growth occurs when cartilage is young and pliable
C. Perichondrial cells differentiate into chondroblasts
D. Growth occurs during childhood

Answer

### Step-by-Step Solution:

1. **Understanding Cartilage**: Cartilage is a flexible connective tissue found in various parts of the body, including joints, the rib cage, ear, nose, and intervertebral discs. It is composed of cells called chondrocytes, which are embedded in a matrix of collagen fibers and proteoglycans.

2. **Analyzing the Options**:
- **Option 1**: Reactivation of pre-existing chondrocytes takes place in cartilage.
- **Option 2**: Cartilage growth occurs when it is young and pliable.
- **Option 3**: Pericondrial cells of the cartilage differentiate into chondroblasts.
- **Option 4**: Cartilage growth occurs during childhood.

3. **Evaluating Each Option**:
- **Option 1**: This option states that pre-existing chondrocytes can be reactivated. This is true, especially during processes like endochondral ossification, where quiescent chondrocytes become active to form articular cartilage.
- **Option 2**: This option suggests that cartilage growth occurs when it is young and pliable. While cartilage is indeed more pliable when young, it does not continue to grow indefinitely; it is gradually replaced by bone during development.
- **Option 3**: This option claims that pericondrial cells differentiate into chondroblasts. However, pericondrial cells actually differentiate into chondrocytes, not chondroblasts.
- **Option 4**: This option states that cartilage growth occurs during childhood. While cartilage is present, it is primarily replaced by bone through ossification during this period.

4. **Conclusion**: After analyzing all the options, it is clear that **Option 1** is the correct answer because it accurately describes the reactivation of pre-existing chondrocytes during processes like endochondral ossification.