若某学校要从5名男生和2名女生中选出3人作为上海世博会的志愿者，则选出的志愿者中男女生均不少于1名的概率是（ ）
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由题意知本题是一个古典概型，
试验发生包含的事件是从7人中选3个人，共有C73种结果，
满足条件的事件是选出的志愿者中男女生均不少于1名，
需要分两类：1男2女或2男1女，共有C51C22+C52C21种结果，
∴所求概率为
=C 15
+C 22 C 25 C 12 C 37
．5 7
故选A
| 完形填空。 | ||||
| With a determined (坚定的) look on his face, Chicago's Michael McCarthy held on to the banister (扶手) and climbed to the top of the Willis Tower not long ago. The Tower stands 1,451 feet (442 meters) tall, the 1 building in the US. As he got to the last step, McCarthy 2 fell down, but that didn't stop him. The 14-year-old boy finally finished climbing the 2,109 steps and arrived at the top, where he 3 cheers from many people. "I just want to show people that 4 a kid with no legs can do it, anyone can do it," McCarthy said. McCarthy, who was born without legs, has to wear prosthetic legs (假肢) and use a stick to walk. But McCarthy has a strong 5 . He believes having a disability (残疾) shouldn't stop anyone 6 achieving his or her success. He has been in a special school 7 he was four. When he decided to climb the Willis Tower, his teacher, Jeff Kohn, was 8 by his determination (决心) and offered to help train him. They 9 more than ten hours practicing climbing stairs and keeping balance with the prosthetics and sticks on the steps every day." 10 seems that he never knows how difficult it is. 11 I was so tired that I asked him to rest for a day," said Kohn."But he said he was still full of energy and wanted more 12 ." Kohn always walked with McCarthy for the climb."I 13 the last 10 floors, he went faster," said Kohn. "He's the most craven sportsman I've ever trained." McCarthy said he was 14 of himself and that the tower now holds special meaning. "When I'm older, I'll 15 to the building and say 'Look at this building I climbed," he said. | ||||
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