Which of the following is a true contrast of osteoarthritis (OA) and rheumatoid arthritis (RA) ?
a. OA is wear and tear on the joints while RA is an autoimmune disease.
b. RA is a wear and tear on the joints and OA is an autoimmune disease.
c. Both OA and RA are autoimmune diseases.
d. OA has inflammation, pain and stiffness, while RA does not.