2. 外语
  3. Why is space left between the rails of a railway line where one piece joins the next? The space 【B1】 to let the rail 【B2】 when i

Why is space left between the rails of a railway line where one piece joins the next? The space 【B1】 to let the rail 【B2】 when i

admin2009-05-15  98
问题     Why is space left between the rails of a railway line where one piece joins the next? The space 【B1】 to let the rail 【B2】 when it gets hot. On a hot day, the metal expands and if it 【B3】 to do this, the rails would bend 【B4】 shape. This caused railway 【B5】 in the past 【B6】 solids expand much less than liquids or gases, the 【B7】 increases can add up to a lot, when there are long.
【B8】 of rail. For example, the difference in length of rail, in summer and winter, 【B9】 the distance between London and Edinburgh, is about 1/4 mile.
    We 【B10】 keep in our minds and must not forget the expansion of metal when we build a very long metal bridge 【B11】 . So spaces are left in the places 【B12】 the metal is joined.
    When a solid gets colder, it becomes smaller in 【B13】 We can make use of the 【B14】 that solids expand when they 【B15】 , and become smaller in size then they 【B16】 colder.
    For example, when an iron band has to fit tightly round a wooden wheel, first we make it 【B17】 than the wheel, then we 【B18】 it, so that it goes on 【B19】 . When it gets colder, it becomes smaller in size and 【B20】 the wheel very tightly.
选项 A、leaves
B、is left
C、left
D、has left
答案B
解析 space和leave的关系是被动的，故用被动语态。故本题答案为B。
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