古之学者必有师。（1）师者，所以传道受业解惑也。人非生而知之者，孰能无惑？惑而不

提速转向架为什么采用两级刚度弹簧？

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．towns

B．countryside

C．cities

D．farms

（）ですね。いちにちに一回ちゅうしゃしてください。

A.風

B.風邪

C.咳

D.咳邪

对河南省某行政公署的具体行政行为不服申请的复议，由下列哪个机关管辖？ （ ）

A．该行政公署

B．该行政公署法制部门

C．河南省人民政府

D．河南省人民政府法制局

简述生物除磷原理。