问题 单项选择题 A1/A2型题

减少和排除散射线的方法中,下列哪项错误()

A.缩小照射野

B.用金属后背盖的暗盒

C.用遮线筒或缩光器来

D.选择高电压摄影的方法

E.使用滤线栅

答案

参考答案:D

解析:管电压越高,X线的能量越大,容易产生二次射线,散射量就越大。缩小照射野,使用遮线器,减少了原发射线,相应地较少了散射线,使用滤线栅就是吸收散射线。

阅读理解

阅读理解。

     People living in different countries made different kinds of words. Today there are about fifteen hundred

  languages in the world. Each contains many thousands of words A very large dictionary, for example,

 contains four or five hundred thousand words. But we do not need all these. To read short stories you

 need to know only about two thousand words. Before you leave school, you will learn only one thousand

  or more.

     The words you know are called your vocabulary. You should try to make your vocabulary bigger.

 Read as many books as you can. There are a lot of books written in easy English for you to read. You will

  enjoy them. When you meet a new word, find it in your dictionary. Your dictionary is your most useful

 book.      

1. The number of different languages spoken is about _____.

    A. 150          

    B. 15 000              

    C. 500                

    D. 1500 

2. Before you leave your school, you'll learn _____.

    A. only two thousand words                    

    B. five hundred thousand words

    C. more than one thousand words              

    D. three or four thousand words

3. To make you vacabulary bigger, you must _____.   

    A. get as many dictionaries as you can      

    B. read as many books as you can

    C. buy a lot of books              

    D. have a very large English dictionary

4. You will enjoy_____.       

    A. the books written in easy English            

    B. your dictionary

    C. your new words                        

    D. finding new words in a dictionary

5. From the passage we know that one_____ if he knows abut two thousand words

   A. can read long difficult stories      

    B. can read easy short stories

    C. can read as many books as he likes      

    D. will find the dictionary not useful

单项选择题