A 69-year-old client asks the nurse what the difference is between osteoarthritis (OA) and rheumatoid arthritis (RA). Which response is correct ？（）
A．OA is a noninflammatory joint disease. RA is characterized by inflamed, swollen joints.
B．OA and RA are very similar. OA affects the smaller joints, and RA affects the larger, weight-bearing joints.
C．OA affects joints on both sides of the body. RA is usually unilateral.
D．OA is more common in women. RA is more common in men.
