■ Section B Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished sentences. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice. Passage One Questions 21 to 25 are based on the following passage. During the past seven or eight years, researchers have made some new and exciting discoveries about osteoarthritis (骨关节炎), a common and debilitating problem. No longer considered an inevitable consequence of the wear and tear associated with aging, osteoarthritis is now understood to be an active process that progressively damages cartilage (软骨) , the normally resilient (有弹性的) connective tissue cushioning every joint in the body. Osteoarthritis is caused by damaged cartilage that the body cannot properly repair. As we age, our cartilage becomes more prone to damage. When this damage occurs, cells within the cartilage may release mediators (substances that cause local inflammation), along with other cartilage-destroying chemicals. This process of damage upon more damage results in osteoarthritis. Researchers have been able to identify what puts people at risk of developing osteoarthritis. Age is not necessarily an issue, although the disease is certainly more common in the elderly. Obesity is an overwhelmingly strong risk factor. For those already diagnosed, losing weight has been shown to slow the disease’s progression and substantially ease joint pain. Injury to a bone or joint may make that area more prone to arthritis in the future. For example, ankle fractures and knee surgery are linked to osteoarthritis, as are injuries due to some vigorous contact sports. Repetitive activities such as the movements involved in certain fields of work can contribute to osteoarthritis. A number of recent studies have emphasized the importance of exercise in reducing pain and maintaining function in people with osteoarthritis. Weight reduction is another key component of treatment. Shoe inserts and knee braces can also relieve knee pain caused by osteoarthritis. Although basic pain medications can help, non-steroidal anti-inflammatory drugs such as ibuprofen (布洛芬，一种抗炎、镇痛药) are more effective in relieving pain. However, these drugs carry the risk of kidney damage, high blood pressure, fluid retention and stomach bleeding. Glucosamine sulfate (氨基葡萄糖硫酸盐) is a component of normal joint cartilage. Recent studies have shown that 1,500 mg per day of this medication, available without a prescription, can decrease pain and improve function for patients with osteoarthritis of the knee. 第22题：According to the passage, osteoarthritis ________. A) is inevitably caused by wear and tear due to aging B) is an active process in which cartilage is damaged abruptly C) is caused by damaged cartilage that the body cannot properly repair D) is caused by cells within the cartilage that may release mediators