听力原文： It's common knowledge that music can have a powerful effect on our emotions. In fact, since the 1930s, music therapists have relied on music to calm patients and help control pain. Now psychologists are confirming that music can also help relieve depression and improve concentration. For instance, in a recent study, 50 surgeons were given some high-stressed math problems to solve. They were divided into three groups: one worked in silence, and in another, the surgeons listened to music of their choice on headphones the third group listened to classical music chosen by the researchers. The results of the study may surprise you. The doctors who got to choose their own music experienced less stress and scored better than the others. One possible explanation is that listening to the music you like stimulates Alfa waves in the brain, increases heart rate and expands breathing. That helps to reduce stress and sharpen concentration. Other research suggests a second relationship between music and the brain: By examining the blood of students after they listened to a variety of classical music selections, researchers found that some students showed a large increase in endorphin, a natural pain reliever. This supports what music therapists have known for years: Music can help revitalize or calm the patient. Questions 26 to 29 are based on the passage you have just heard． (33)