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问题 选择题
在下 * * 个式子①ab=0；②a+b=0；③
a
b
=0；④a2=0；⑤a2+b2=0中，a一定是零的式子有（　　）个．
A．2B．3C．4D．5
答案

①当a≠0，b=0时ab=0，故此小题错误；

②若a=-2，b=2，则a+b=0，故此小题错误；

③只有a=0时，

a
b
=0，故此小题正确；

④只有a=0是，a2=0，故此小题正确；

⑤只有a=0，b=0时，a2+b2=0，故此小题正确．

所以③④⑤三个．

故选B．

阅读理解

阅读理解。

     My name is Xu Fei.  I'm in No.  9 Junior High School in Jinan.  I have a friend.  His name is Zhang

 Hua.  He's from Hunan, but now he is in Jinan with his mom.

     Zhang Hua is in Class 3, Grade 7 in Xiwang Junior High School in Jinan.  He likes math (数学) and it is

  good, but his English is poor.  Miss Chen, his English teacher, helps (帮助) him after class (课后).  

 Zhang Hua has a cat (猫) at home.  It's white and black.  Feifei is its (它的) name.  He likes the cat.  

1.  Where does Zhang Hua come from?

    A.  Xiwang        

    B.  Jinan          

    C.  Hunan

2.  划线单词poor的意思应该是: _____

    A.  good          

    B.  not good        

    C.  OK

3. Who helps Zhang Hua with his English?

    A.  Miss Chen    

    B.  Xu Fei          

    C.  Zhang Hua's mom

4. What color is the cat?

    A.  Black.        

    B.  White.          

    C.  White and black.

5. 根据文章内容,下列说法正确的是: _____

    A.  Xu Fei is in Xiwang Junior High School. 

    B.  Zhang Hua is 15. 

    C.  The cat's name is Feifei
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多项选择题

海洋能包括

A.气浪能 

B.水流能 

C.潮汐能 

D.波浪能 

E.海流能
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