问题
填空题
函数f(x)=
|
答案
x=1时f（1）=1，x=2时，f(2)=
，x=3时，f(3)=1 2 1 3
故答案为{1，
，1 2
}1 3
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函数f(x)=
|
x=1时f（1）=1，x=2时，f(2)=
，x=3时，f(3)=1 2 1 3
故答案为{1，
，1 2
}1 3
| 完形填空。 | |||
| Villagers are more healthy than people who live in towns. Orie reason for this is that country air is fresher than the air in 1 . The villager breathes fresh clean air all day in the fields, but the air the townsman 2 is always full of smoke and dust. We can't live without air. If we are stopped from breathing 3 for five minutes, we will die. Bad air means bad health and certain kinds of 4 , which may kill us in the end, 5 they may not kill us at once. We all 6 what unpleasant feelings we get if we stay a long time in a shut, crowded room. After a time, we begin to feel very 7 , and can hardly keep our eyes open. Then our heads begin to ache, and the longer we stay, the worse we feel. How nice it is when we get 8 into the fresh air outside. We must, therefore, keep our windows open, so that the 9 in our houses is always fresh, and we should breathe as much as we can in the open air. For people who breathe 10 air for a long time often get very ill and die of lung diseases. | |||
| ( )1. A. factories ( )2. A. breathes ( )3. A. still ( )4. A. experience ( )5. A.so ( )6. A.imagirle ( )7. A. sleepy ( )8. A. up ( )9. A. air ( )10 . A. humid | B. cities B. eats B. as B. stress B.though B.know B.lonely B. down B. environment B. clean | C. streets C. takes C. even C. death C. since C. fear C. energetic C. out C. furniture C. open | D. fields D. smells D. except D. illness D. also D. expect D. exhausted D. off D. wind D. bad |