The ribs articulate with the :

Options

A. thoracic vertebrae
B. sacrum
C. cervical vertebrae
D. lumbar vertebrae

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks with which part of the skeleton the ribs articulate. The options provided are thoracic vertebra, sacrum, cervical vertebra, and lumbar vertebra.

2. **Identifying the Correct Option**:
- Ribs primarily articulate with the **thoracic vertebrae**. This is the key point to focus on.

3. **Explaining the Articulation**:
- Each rib articulates with the thoracic vertebrae through two types of joints:
- **Costovertebral Joint**: This joint involves the head of the rib articulating with the vertebrae at three points:
- The **superior costal facet** of the corresponding thoracic vertebra.
- The **inferior costal facet** of the vertebra above it (the superior vertebra).
- The **intervertebral disc** that separates the two vertebrae.
- **Costotransverse Joint**: This joint is formed by the articulation of the **transverse process** of the thoracic vertebra and the **tubercle** of the adjacent rib.

4. **Eliminating Incorrect Options**:
- **Sacrum**: Incorrect, as ribs do not articulate with the sacrum.
- **Cervical Vertebra**: Incorrect, as ribs do not articulate with cervical vertebrae.
- **Lumbar Vertebra**: Incorrect, as ribs do not articulate with lumbar vertebrae.

5. **Conclusion**: The ribs articulate with the **thoracic vertebrae**. Therefore, the correct answer is option 1: thoracic vertebra.