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问题 选择题

下列物质中，属于纯净物的是（　　）

A．硫酸锌

B．石油

C．空气

D．海水

答案

A、硫酸锌是由一种物质组成的，属于纯净物，故选项正确；

B、石油中含有汽油、煤油等多种物质，属于混合物，故选项错误；

C、空气中含有氮气、氧气等物质，属于混合物，故选项错误；

D、海水中含有氯化钠、水等多种物质，属于混合物，故选项错误；

故选项为：A．

判断题

当储集层的电阻率大于油层最小电阻率时。该层可判断为水层。
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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（5）空应选择（）

A．spent

B．purchased

C．wounded

D．burnt
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