15.By “just the tip of the iceberg” (Line 2, Para. 8), Siegel suggests that .

　　A) half-brain sleep has something to do with icy weather

　　B) the mystery of half-brain sleep is close to being sleepers

　　C) most birds living in cold regions tend to be half sleepers

　　D) half-brain sleep is a phenomenon that could exist among other species

　　Passage Two

　　Questions 16 to 20 are based on the following passage.

　　A nine-year-old schoolgirl single-handedly cooks up a science-fair experiment that ends up debunking(揭穿…的真相)a widely practiced medical treatment. Emily Rosa’s target was a practice known as therapeutic(治療的)touch(TT for short), whose advocates manipulate patients’ “energy field” to make them feel better and even, say some, to cure them of various ills. Yet Emily’s test shows that these energy fields can’t be detected, even by trained TT practitioners(行醫(yī)者). Obviously mindful of the publicity value of the situation, Journal editor George Lundberg appeared on TV to declare, “Age doesn’t matter. It’s good science that matters, and this is good science.”

　　Emily’s mother Linda Rosa, a registered nurse, has been campaigning against TT for nearly a decade. Linda first thought about TT in the late ‘80s, when she learned it was on the approved list for continuing nursing education in Colorado. Its 100,000 trained practitioners (48,000 in the U.S.) don’t even touch their patients. Instead, they waved their hands a few inches from the patient’s body, pushing energy fields around until they’re in “balance.” TT advocates say these manipulations can help heal wounds, relieve pain and reduce fever. The claims are taken seriously enough that TT therapists are frequently hired by leading hospitals, at up to $70 an hour, to smooth patients’ energy, sometimes during surgery.

　　Yet Rosa could not find any evidence that it works. To provide such proof, TT therapists would have to sit down for independent testing-something they haven’t been eager to do, even though James Randi has offered more than $1 million to anyone who can demonstrate the existence of a human energy field. (He’s had one taker so far. She failed). A skeptic might conclude that TT practitioners are afraid to lay their beliefs on the line. But who could turn down an innocent fourth-grader? Says Emily: “I think they didn’t take me very seriously because I’m a kid.”

　　The experiment was straightforward: 21 TT therapists stuck their hands, palms up, through a screen. Emily held her own hand over one of theirs─left or right─and the practitioners had to say which hand it was. When the results were recorded, they’d done no better than they would have by simply guessing. If there was an energy field, they couldn’t feel it.

　　16. Which of the following is evidence that TT is widely practiced?

　　A) TT has been in existence for decades.

　　B) Many patients were cured by therapeutic touch.

　　C) TT therapists are often employed by leading hospitals.

　　D) More than 100,000 people are undergoing TT treatment.

　　17. Very few TT practitioners responded to the $1 million offer because .

　　A) they didn’t take the offer seriously

　　B) they didn’t want to risk their career

　　C) they were unwilling to reveal their secret

　　D) they thought it was not in line with their practice

　　18. The purpose of Emily Rosa’s experiment was .

　　A) to see why TT could work the way it did

　　B) to find out how TT cured patients’ illnesses

　　C) to test whether she could sense the human energy field

　　D) to test whether a human energy field really existed

　　19. Why did some TT practitioners agree to be the subjects of Emily’s experiment?

　　A) It involved nothing more than mere guessing.

　　B) They thought it was going to be a lot of fun.

　　C) It was more straightforward than other experiments.

　　D) They sensed no harm in a little girl’s experiment.