Question 21 is based on the recording you have just heard.

       The thin, extremely sharp needles didn’t hurt at all going in. Dr. Gong pierced them into my left arm, around the elbow that had been bothering me. (19) Other needles were slipped into my left wrist and, strangely, into my right arm, and then into both my closed eyelids.

     There wasn’t any discomfort, just a mild warming sensation. However, I did begin to wonder what had driven me here, to the office of Dr. James Gong in New York’s Chinatown. Then I remembered—the torturing pain in that left elbow. (20) Several trips to a hospital and two expensive, uncomfortable medical tests had failed to produce even a diagnosis. “Maybe you lean on your left arm too much,” the doctor concluded, suggesting I see a bone doctor. During the hours spent waiting in vain to see a bone doctor, I decided to take another track and try acupuncture. A Chinese-American friend recommended Dr. Gong. I took the subway to Gong’s second-floor office marked with a hand-painted sign. Dr. Gong speaks English, but not often. Most of my questions to him were greeted with a friendly laugh, but I managed to let him know where my arm hurt. He asked me to go into a room, had me lie down on a bed, and went to work. In the next room, I learned a woman dancer was also getting a treatment. As I lay there a while, I drifted into a dream-like state and fantasized about what she looked like.

       Acupuncturists today are as likely to be found on Park Avenue as on Mott Street. In all, there are an estimated 10,000 acupuncturists in the country. Nowadays, a lot of medical doctors have learned acupuncture techniques; so have a number of dentists. (21) Reason? Patient demand. Few, though, can adequately explain how acupuncture works. Acupuncturists may say that the body has more than 800 acupuncture points. A life force called qi circulates through the body. Points on the skin are energetically connected to specific organs, body structures and systems. Acupuncture points are stimulated to balance the circulation of qi. “The truth is, though acupuncture is at least 2,200 years old, nobody really knows what’s happening,” says Paul Zmiewski, a Ph.D. in Chinese studies who practices acupuncture in Philadelphia.

      After five treatments, there has been dramatic improvement in my arm, and the pain is a fraction of what it was. The mainly silent Dr. Gong finally even offered a diagnosis for what troubled me. “Pinched nerve,” he said.

21. What accounts for the growing popularity of acupunture in the United States according to the speaker??

解析：A。根据讲座中的“Patient demand”可知，针灸在美国越来越受欢迎，原因就在于患者的需求。因此正确答案为A项。