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标题: 四级练习2016.02.25 [打印本页]

作者: Rebecca949    时间: 2016-3-1 09:17     标题: 四级练习2016.02.25

[audio]http://sound.yywz123.com/tingbbs/cet4/cet420160225.mp3[/audio]


M:  Want to go out and get something to eat?
W:  I can't.I have a chemistry midterm on Monday and a German exam on Tuesday.
M:  I have a geology exam Monday myself,but I think I'm ready for it.
W:  What kind of exam is it going to be multiple choice or essay?
M:  Neither.The professor is going to give us a mineral sample and we have to identify it.
W:  How do you do that? I mean,a rock's a rock,isn't it?
M:  Actually,there are a lot of tests you can perform on minerals to help you figure out what they are.Probably the first tests I'll do are scratch tests.(1)_______________________.That tells you the relative hardness of the sample.
W:  What other tests will you do?
M:  I'll probably do a streak test next.In that test,you rub an unknown mineral against a piece of china to see what color the streak is.
W:  Why can't you just look at the mineral to see what color it is?
M:  (2)_______________________.But a streak test shows the mineral's true color. Then there's always the specific gravity test,the blowpipe test...oh,and...
W:  And after you've done all these tests,can you positively identify any mineral?
M:  Well, usually...but not always.(3)___________________



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