Answer
(d) rheumatoid arthritis
Work Step by Step
As rheumatoid arthritis develops, synovial fluid accumulates, causing joint swelling. In time, the inflamed synovial membrane thickens into a pannus, an abnormal tissue that clings to the articular cartilages. The pannus erodes the cartilage (and sometimes the underlying bone) and eventually scar tissue forms and connects the bone ends. Later this scar tissue ossifies and the bone ends fuse together, immobilizing the joint (page 272).
