若平面α⊥平面β，直线n⊂α，m⊂β，m⊥n，则（ ）
A．n⊥β
B．n⊥β且m⊥α
C．m⊥α
D．n⊥β与m⊥α中至少有一个成立
若平面α⊥平面β，直线n⊂α，m⊂β，m⊥n
①若m垂直平面α与平面β的交线，此时m⊥α，n与β关系不确定；
②若n垂直平面α与平面β的交线，此时n⊥β，m与α关系不确定；
③假设m，n均不垂直于平面α与平面β的交线，
则过m上不在交线上一点O，做平面α与平面β的交线的垂线l，
则l⊥α，则l⊥n，由于l∩m=O，l⊂β，m⊂β，则n⊥β
此时n⊥平面α与平面β的交线
这与假设矛盾，故m，n至少有一条与平面α与平面β的交线垂直，
由n⊥β与m⊥α中至少有一个成立
故选D
British and American scientists are raising genetically modified(转基因的) pigs in the hope of providing organs for transplant(移植) to humans, the project leader wrote in a newspaper Sunday. Scientists in London and California have begun conducting the genetic experiments to find a solution to record–long waiting lists for organ transplants, Robert Winston said in an opinion piece written for Britain's Sunday Times. In Britain alone, around 8,000 patients are waiting for a transplant. "People needing a new heart or liver are waiting for someone else to die – usually a violent death in a traffic accident," Winston wrote in the newspaper. He said his team was "trying to modify pigs so their organs might save the lives of humans." The scientists are introducing human genes into the animals to reduce the chances of the organs being rejected by patients, as has been common in previous attempts to use animal tissues, said Winston, who heads the Institute of Reproductive and Developmental Biology at London's Hammersmith Hospital. Working with Dr. Carol Redhead of the California Institute of Technology, Winston's team has injected human genes directly into male piglets(猪仔), adding them to the animal's sperm(精子). He said that pigs involved in experiments had successfully produced transgenic sperm, but acknowledged that British and European laws had prevented the team from using the pigs to mate. The Sunday Times newspaper reported that the experiments would be moved to the United States following difficulties with funding and regulations in Britain. It said the pigs would be bred in Missouri. "Our U.S. friends will benefit from our technology and the income we might have produced for Britain will be lost," Winston wrote. Some scientists have previously blamed the idea of using animal organs for human transplant, saying the technique risks spreading animal viruses to humans. Winston said his research project is attempting to breed virus-free pigs. 49. Scientists are introducing human genes into the animals to ____________.
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