72．In the third paragraph, by saying “though there is no proof that this is the case”, the writer means that .

　　A．students in single-sex schools will certainly become homosexual

　　B．students in co-educational schools cannot have extreme opinions

　　C．students in co-educational schools are likely to be homosexual

　　D．single-sex school conditions may or may not have effects on the students

　　【实战演练练习十四】（04 重庆卷 D 篇）

　　Have you ever had the strange feeling that you were being watched? You turned around and, sure enough, someone was looking right at you!

　　Parapsychologists (灵学家) say that humans have a natural ability to sense when someone is looking at them. To research whether such a “sixth sense”really exists, Robert Baker, a psychologist(学家)at the University of Kentucky, performed two experiments.

　　In the first one, Baker sat behind unknowing people in public places and stared at the backs of their heads for 5 to 15 minutes. The subjects（受试者）were eating, drinking, reading，studying, watching TV, or working at a computer. Baker made sure that the people could not tell that he was sitting behind them during those periods. Later, when he questioned the subjects, almost all of them said they had no sense that someone was staring at them.

　　For the second experiment, Baker told the subjects that they would be stared at from time to time from behind a two way mirror in a laboratory setting. The people had to write down when they felt they were being stared at and when they weren’t. Baker found that the subjects were no better at telling when they were stared at and when they weren’t .Baker found that the subjects were no better at telling when they were stared at than if they had just guessed.

　　Baker concludes that people do not have the ability to sense when they’re being stared at. If people doubt the outcome of his two experiments, said Baker, “I suggest they repeat the experiments and see for themselves.”