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【简答题】
Many of us don't pay much attention to the importance of eye care. It is said that if you take care of your body, then you can surely be healthy. That is why our eyes should be given a lot of care. Natural eye care should be put in a number one place. There are several causes leading to poor eyesight like not enough food, genes (基因) and aging (老化). Televisions, computers and reading are also the causes of having poor eyesight. If you happen to work in front of the computer, it is best to take a break every once in a while. Something dirty can cause redness and they will make you feel uncomfortable. It is bad for your eyes, too. If this happens, the best way is to clean your eyes by using cold water. You must also try your best to protect your eyes from harmful things. For example, sunglasses are not just for fashion but they can also serve as a great way to protect your eyesight form UV rays. Eating healthy foods will do good to your eyesight. Remember that vitamins A, C and E are good for eyes. Try to eat food groups that have these vitamins. And you should do eye exercises because exercise protects your eyesight, too. If a person exercises regularly (定期地) and eats the right kind of food, his eyes will stay in good condition for a long time. All above are natural ways of eye care that help us keep healthy eyes. Being happy all the time can be helpful to a person's eyesight, too. In a word, eye care is very important, no matter how old a person is. 小题1:_____ is the most important way to protect our eyes. A.Seeing the doctor B.Taking medicine C.Natural eye care D.Being happy all the time 小题2:All the following causes can lead to bad eyesight except _______. A.age B.height C.reading D.computers 小题3:What should you do if you have to work in front of the computer? A.Eat healthy foods. B.Have a rest after working for a while. C.Wear a pair of sunglasses. D.Clean the eye by using cold water 小题4:Which is the best title of the passage? A.Ways of Being Happy B.Ways of Eye Exercises C.Ways of Eye Care D.Ways of Being Healthy
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参考答案:
举一反三
【判断题】已知E(X)=2,E( )=6,则D(1-3X)=18
A.
正确
B.
错误
【简答题】Part 4: Para 12-15
【单选题】已知随机变量X的期望E(X)=-1,方差D(X)=3,则E[3(X 2 -2)]=(    ).
A.
9  
B.
6  
C.
30
D.
36
【简答题】已知E(X+2)=6, ,则D(X)=____.
【单选题】已知函数 f(x)=lo g 2 ( x 2 -2x-3) ,给定区间E,对任意x 1 ,x 2 ∈E,当x 1 <x 2 时,总有f(x 1 )>f(x 2 ),则下列区间可作为E的是(  )
A.
(-3,-1)
B.
(-1,0)
C.
(1,2)
D.
(3,6)
【判断题】切削力的大小对工件是否打滑没有影响。
A.
正确
B.
错误
【单选题】已知E(X)=-1,D(X)=3,则E[3(X 2 -2)]=(    ).
A.
9  
B.
6  
C.
30
D.
36
【简答题】What is the main idea of Part Three(para.15--para.17)?
【单选题】已知 B =(2z-3y) e x +(3x-z) e y +(y-2x) e z ,则相应的 J 等于 ( ) 。 A. (-2 e x -4 e y -6 e z ) B. (2 e x +4 e y +6 e z )μ C. (2 e x +4 e y +6 e z ) ...
A.
B.
C.
D.
D
【判断题】切削力的大小对工件是否打滑没有影响。
A.
正确
B.
错误
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