Ilio-sacral joint is :-

Options

A. Fibrous joint
B. Cartilaginous joint
C. Hinge joint
D. Synovial joint

Answer

### Step-by-Step Solution:

1. **Identify the Joint**: The ilio-sacral joint, also known as the sacroiliac joint, is the joint in question.

2. **Location of the Joint**: This joint is located between the ilium (the uppermost part of the hip bone) and the sacrum (the triangular bone at the base of the spine).

3. **Type of Joint**: The ilio-sacral joint is classified as a synovial joint.

4. **Characteristics of Synovial Joints**: Synovial joints are characterized by the presence of a synovial cavity filled with synovial fluid, which lubricates the joint and allows for smooth movement between the articulating surfaces.

5. **Examples of Other Joints**: Other types of joints include:
- Hinge joints (e.g., elbow and knee)
- Cartilaginous joints (e.g., joints between vertebrae)
- Fibrous joints (e.g., joints in the cranium)