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问题 选择题

下列现象中，可以用光沿直线传播解释的是（　　）

A．树在水中的倒影

B．立竿见影

C．冰透镜向日取火

D．鱼翔浅底

答案

A、树在水中的倒影是平面镜成像形成的，平面镜成像的原理是光的反射；

B、立竿见影是影子，影子是光的直线传播形成的；

C、冰透镜就是一个凸透镜，可以利用光的折射将太阳光会聚在一点上，从而起到取火的目的；

D、鱼翔浅底，由于光的折射，所以池底看起来好像变浅了．

故选B．

多项选择题

信用证是银行出具的一种有条件的付款保证，关于信用证的业务特点，说法正确的有（）。

A．信用证是一种银行信用

B．信用证是一种商业信用

C．信用证是一种自足文件

D．信用证是一种单据业务

E．信用证是一种结算方式
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单项选择题

Until recently, most population growth has occurred in relatively dense urban environments. In (91) words, even if we were witnessing rapid population growth, that would not mean that the (92) were filling in with people. (93) , the urban areas would tend to become more crowded. Historically, we find that people have moved to (94) the jobs were. Jobs were usually in ports or locations with many natural (95) . After transportation became relatively cheap, other geographical locations became (96) of economic activity. One factor that determines where people will move to, even when transportation becomes cheap, is (97) . And individuals working in cities (98) higher incomes than those working in (99) areas. Hence, population has tended until the 1970s to (100) in our major urban centers. Recently population has (101) out of the Northeast to the South and to the West for the more pleasant climates. If people did not (102) from living in large cities, there would likely be a much more even population distribution (103) our entire land area. Probably, if this (104) the case, there would be less concern over population (105) Indeed, one need only (106) a cross-country drive or plane trip to realize how (107) populated these United States really are. This is not to say that we should or should not do something about (108) growth. The shortage of people in certain areas merely demonstrates that overpopulation in the United States is really only a problem in (109) urban environments. And this problem may be slowly correcting (110) .

A．withdraw

B．derive

C．develop

D．benefit
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