Joints can be classified by their structures. Which is an example of a cartilaginous joint? The joints that articulate the bones of the skull.
The joints that articulate the bones of the spine.
The joints that articulate the bones of the pelvis.
The joints that articulate the bones of the legs.

Examples of cartilage joints are the joints that articulate the bones of the spine and bones of pelvis.

Explanation:

Cartilage joints are characterized by the fact that they join the bone surfaces to each other by means of cartilage, providing them with very limited mobility.  The union of the pelvis bones and the one between the vertebrae of the spine are joined by a fibrous cartilage, a representative example of the cartilage joints, called the symphysis.  

The other options are not correct because:

what are the choices?