disease, an uncommon disorder of the immune system(免疫系统), they found it difficult to refuse testing recommended by her doctor. The doctor insisted on office visits every three weeks, even when she was feeling well. He frequently ordered blood tests and X-rays, and repeatedly referred her to experts for even minor complaints. Even when tests came back negative, more were ordered, and she was hospitalized as prevention when she developed a cold. She had as many as 25 doctor visits during one six-month period. The couple was spending about $30,000 a year for her care.

　　After several years of physical suffering and near financial ruin from the medical costs, the couple began questioning the treatment after discussing with other patients in online support groups. "It's a really hard thing to determine when doctors have crossed the line," Mr. Power said. "You think she's getting the best care in the world, but after a while you start to wonder: What is the purpose?" Mr. Power then spoke with his own primary care doctor, who advised him to find a new expert to oversee Mrs. Power's care. Under the new doctor's care, the regular testing stopped and Mrs. Power's condition was stable. Now she sees the doctor only four or five times a year.

28. What is the main idea of this passage?

A. Treatments do not always cause harmful side effects.

B. Patients tend to believe more testing is better treatment.

C. Too much medical care may not be beneficial to patients.

D. Doctors generally recommend office visits that are necessary.

29. Which of the following was a problem for Mrs. Power during her medical treatment?

A. She had to be hospitalized for three weeks whenever she had a cold.

B. When test results showed she was fine, her doctor still ordered more tests.

C. She did not have any insurance, so she became penniless.

D. Her doctor asked her to consult other experts for her complaints.

30. What does "develop" in the second paragraph probably mean?

A. construct B. improve C. catch D. attack

31. When did the Powers start to doubt Mrs. Power's treatment?

A. After knowing about other patients' treatment. B. After analyzing the results of her blood tests.

C. After curing Mrs power of her illness. D. After the new expert's testing

　　　　　　　　　　　　　　　　　　D

The bristlecone pine (狐尾松) is one of the longest-living things on Earth. These trees, with their strangely shaped branches, can live up to 5,000 years, but experts worry that a warming climate in some areas may threaten its future.

Researchers say warmer weather is permitting a similar kind of tree, the limber pine (柔枝松), to take over good growing places from the ancient bristlecone. They say the tree is being forced out of mountainous areas where it grows.

Scientists at the University of California, Davis, say climate change is causing the trees to compete with each other.

Brian Smithers led the research project. "The limber pine is taking all the good spots," he said.

Bristlecone pines grow in high mountain forests in eastern California, Nevada and Utah. In the mountains, they face high winds and extreme temperatures.

The difficult conditions leave the trees with twisted（变形的） branches and shapes. To survive long periods without water, parts of the trees die, including much of their outer bark (外皮). This