2. 外语
  3. A. solid B. made up of C. equal D. fills E. describing F. vapor G. therefore H.

A. solid B. made up of C. equal D. fills E. describing F. vapor G. therefore H.

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问题     A. solid        B. made up of        C. equal         D. fills        E. describing
    F. vapor        G. therefore         H. fundamental   I. elementary   J. distinguished
    K. flow         L. refuting          M. consisted of  N. however      O. dense
    The difference between a liquid and a gas is obvious under the conditions of temperature and pressure commonly found at the surface of the Earth. A liquid can be kept in an open container and【C1】________ it to the level of a free surface. A gas forms no free surface but tends to diffuse throughout the space available; it must【C2】________ be kept in a closed container, as in the case of a planet’s atmosphere. The distinction was a prominent feature of early theories【C3】________ the phases of matter. In the nineteenth century, for example, one theory maintained that a liquid could be "dissolved" in a【C4】________ without losing its identity, and another theory held that the two phases are【C5】________ different kinds of molecules. The theories now prevailing take a quite different approach by emphasizing what liquids and gases have in common. They are both forms of matter that have no permanent structure, and they both【C6】________ easily. They are fluids.
    The【C7】________ similarity of liquids and gases becomes clearly apparent when the temperature and pressure are raised somewhat. Suppose a closed container partially filled with a liquid is heated.
    The liquid expands, or in other words, becomes less【C8】________ ; some of it evaporates. In contrast, the vapor above the liquid surface becomes denser as the evaporated molecules are added to it. The combination of temperature and pressure at which the densities become【C9】________ is called the critical point. Above the critical point the liquid and the gas can no longer be【C10】________ ; there is a single, undifferentiated fluid phase of uniform density.
【C1】
选项
答案D
解析 空格处与上文的can be kept…通过and连接，且空格后接了宾语it，故推断空格处填入及物动词。it指代的是an open container，液体应是“填充”到容器一定的水平面，备选动词中的fills“填充”符合语境要求，故选D。
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