4. A　 in　　　 B. off　　　　　　　　 　　C. out of　　　　　　 D. with

3. A. is not allowed　　　 B. is allowed　　　 C. were not allowed　　 D. were allowed

2. A. hot　　　 B. wet　　　　　　　　　　 C. cold　　　　　　　 D. dry

1. A. leaves　 　B. is left　　　　　　　　　 C. left　　　　　　　 D. has left

25.A.self-satisfaction　 B. self-protection C. self-respect　　　　　 D. self-service

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　　　　 Why is a space left between the rails of a railway line where one piece joins the next? The space　 1　 to let the rail expand (膨胀)when it gets　 2 . On a hot day, the metal expands and if it　 3　 to do this, the rails would bend　 4　 shape. This caused railway　 5　 in the past.

　　　　　 6　 solids expand much less than liquids or gases, the　 7　 increases (增加量) can add up to a lot, when there are long　 8　 of　 rail. For example, the difference in length of rail, in summer and winter,　 9　 the distance between London and Edinburgh, is about 1/4 mile.

　　　　 We　 10　 keep in our minds and must not forget the expansion of metal when we build a very long metal bridge　 11 . So spaces are left in the places　 12　 the metal is joined.

　　　　 When　 13　 colder, it becomes smaller in size. We can make use of the　 14　 that solids expand when they are heated, and become smaller in size when they get colder, and　 15　 they do it at different　 16 .

　　　　 For example, when an iron band (铁箍) has to fit tightly　 17　 a wooden wheel, first we make it　 18　 than the wheel, then we　 19　 it, so that it goes on easily. When it gets colder, it becomes smaller in size and　 20　 the wheel very tightly.

24.A. surprised　 B. admired　　　　　 C. inspired　　　　　　 D. supported

23.A. before　　 B. since　　　　　　　 C. until　　　　　　　 D. when

22.A. followed　 B. caused　　　　　　 C. produced　　　　　 D. ended

21.A. key　　　 B. kettle　　　　　　　 C. door-lock　　　　　 D. wire

20.A. A sad voice　 B. A strange noise　　 C. A warning shout　　 D. A sharp cry