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问题 计算题

南京长江大桥下层铁路桥全长6772m，其中江面正桥长1572m，一列火车上的的乘客测试自己完全通过正桥用了100s，试计算这列匀速行驶的火车完全通过铁路桥的速度是多少？

答案

6.772m/s

填空题

风道继电器风道内无风压或风压低于（）Pa时，动触头在反力弹簧及膜片的作用下恢复到原位。
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单项选择题

Looking back on my childhood, I am convinced (1) naturalists are born and not made. Although we were all brought (2) in the same way, my brothers and sisters soon gave up their pressed flowers and insects. (3) them, I had no ear (4) music and languages, I was not an early reader and I could not do mental arithmetic.Before World War I we (5) our summer holidays in Hungary. I have only the memory of the house we lived (6) , of my room and my toys. I can hardly (7) clearly the large family of grandparents, aunts, uncles and cousins who gathered (8) door. But I do have a clear memory of the dogs, the farm (9) , the local birds and, (10) all, the insects.I am a (11) , not a scientist. I have a p (12) of the natural world, and my enthusiasm has led me into varied investigation. I love discussing my favorite topics and enjoy (13)  the midnight oil  (14)  reading about other people’s observations and discoveries. Then  (15)  happens that brings these observations together  (16)  my conscious mind. Suddenly you fancy (想象), you see the answer  (17)  the riddle, and books, of which some might honor with the title of scientific research.But curiosity, a keen eye, a good memory and enjoyment of the animal and plant world do not make a scientist; one of the outstanding and essential  (18)  required is self-discipline, a quality I lack. A scientist requires not only  (19)  but also hard training, determination and a goal. A scientist, up to a point, can be made. A naturalist is  (20) . If you can combine the two, you get the best of both worlds.

 

 

第（20）空应选择（）

A．made

B．born

C．produced

D．found
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