阅读理解。
Americans love sports-they love to play them, to watch them on televisions, and to talk about them. But this hobby sometimes has serious results-at least to the players. For example, when people play tennis, sometimes they hurt their elbow and in this way they develop "tennis elbow". Also it is easy to hurt knees in
a football game. These injuries happen while the player is having fun, but they still hurt. A few months ago, Kathleen
Simmons, who loves playing volleyball, hurt her knee in a volleyball game. Her doctor told her that she needed a very difficult operation (手术) or she might not be able to play again,
She felt very sad and didn't know what to do. Then Simmons learned about "video operation". With the help of this new science in medicine, doctors can now repair many injuries and get people back on the playing field and back to their jobs much faster. Simmons found a hospital that was using this new science and went to see the doctors there. The doctors told her the operation could help. For this operation, her doctor didn't have to open her knee. Instead he put a very small camera lens (镜头) inside her knee. The lens sent back pictures, which appeared on a television screen. As he worked, he could see the inside of her knee
on the TV. With the help of the large pictures on the screen, the doctor knew exactly what to do when he was making the repairs.
Simmons started walking five days after her operation. " My knee hurt a lot the first few days," she
said. "But I felt better very quickly. " Now, six months after her operation,
Simmons can do everything she did before her injury. "It feels like a new knee," she said. "I can even
play volleyball again. "
根据短文内容，回答下列问题 。
1. Do Americans love sports?
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2. What sport is Simmons interested in?
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3. What did the doctor put inside Simmons' knee?
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4. What problem may people have when they play sports?
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5. What's the advantage of the new science?
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→①→②→⑤→⑥→⑦”，所涉及的作业有A、B、D、E、P。通过表4-14的第3列可知，作业A完成测试所花费的天数允许缩短1天，即由原来的2天变为1天。同理，作业B、D、E分别允许缩短2天、1天、2天的测试时间，但作业P不允许缩短测试时间。 3) 通过表4-14的第4列可知，在作业A、B、D、E中，作业A是缩短1天测试时间所需增加费用最少(500元)的作业。如果将测试作业A缩短1天，则在图4-8中路径“→①→②→⑥→⑦”所花费的时间变为18天；路径“
→①→②→⑤→⑥→⑦”所花费的时间变为19天；路径“
→①→③→④→⑥→⑦”所花费的时间变为18天，完成该测试项目计划需要19天。可见，将测试作业A缩短1天就能满足试题要求。 4) 由以上分析可知，将测试作业A缩短1天后，该测试项目计划的关键路径仍为“
→①→②→⑤→⑥→⑦”。