患者诉肛内剧痛，指诊触及齿线上直肠粘膜明显隆起，并有波动感者选用（） A.低位脓肿切

《煤矿安全规程>规定，一个矿井中只要有( )个煤(岩)层发现瓦斯，该矿井即为瓦斯矿井。

A．1

B．2

C．3

D．4

静脉血中CO主要以下列哪种形式存在()

A．碳酸氢盐

B．碳酸

C．碳酸盐

D．溶解的CO

E．CO与血红蛋白结合

甲、乙两物体的比热容之比是3：1，质量之比是3：1，当它们吸收相同的热量后，甲物体温度升高10℃，则乙物体的温度升高______℃．（甲、乙两物体状态不变）

适用于有效成分遇热易破坏的中药提取，但浸出效率较差

A．浸渍法
B．煎煮法
C．回流提取法
D．渗漉法
E．连续提取法

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．vanished

B．drifted

C．shifted

D．escaped