下列说法中，正确的是（ ） A．-53是分式 B．2x2-x+35是分式 C．x2x2

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     In Singapore, many middle school students spend a lot of their time on their studies. Good education

is often regarded as a ticket to success in their future. So many of these students try their best to get a

good mark in their examinations. They have a lot of homework every day and exams are a big headache.

Sometimes some of them are even made to go to remedial(补习的)classes after school.

     Schools run programmes outside school hours. The students can take part in sports and games, music

and dance, hiking and rock-climbing, etc. They are also very active in community service(社区服务).

     In their spare time, most students like to listen to pop music. Hollywood blockbusters(大片). Hong

Kong and Singapore movies are very popular among them. They understand IT very well. Some of them

also spend their free time surfing the Internet, e-mailing their friends, playing computer and video games.

     They sometimes go to cafes, fast-food restaurants, shopping centers and big bookstores.

     So, it looks like life as a middle school student in Singapore is not easy but it is rich and colorful.

1. What is NOT mentioned in the passage?  

A. Schoolwork.    

B. After-class activities.    

C. Subjects        

D. Things to do in the spare time.

2. Why do students work hard at school in Singapore?        

A. Because they have a lot of homework.

B. Because they have to go to remedial classes.

C. Because they want to get a good future.

D. Because they have many outside school activities.

3. What does the underlined sentences mean in the first paragraph?       

A. Students are afraid of exams.   

B. Students have a headache before an exam.

C. Students have too many exams.

D. Students are in poor health because of exams.

4. Programmes outside school hours are ______.        

A. the same as spare time activities      

B. remedial classes after school

C. sports actives        

D. popular among students

5. What do you know from the last sentences?

A. The middle school students live an easy life in Singapore.

B. The middle school students' life in Singapore is amazing.

C. The middle school students' life in Singapore is boring.

D. The middle school students' life in Singapore is hard, but interesting

如图甲所示的电路中，电源电压保持不变，闭合开关后，滑片P由b端滑到a端，电流表示数I与电压表示数U的变化关系如图乙所示，求：

（1）电源电压U和定值电阻R的阻值；

（2）滑动变阻器的最大阻值；

（3）当滑片P在b端时，滑动变阻器消耗的功率．

一氧化氮是汽车尾气中的成分之一，作为一种大气污染物,它是无色气体,难溶于水,密度比空气略大,在空气中能与氧气迅速反应生成红棕色的二氧化氮。在实验室里，收集一氧化氮时可选用的收集方法是           。

毒性药品的包装容器上必须印有（）

A.特殊标志

B.专有标志

C.毒药标志

D.特殊图案

E.毒字

设X为整型变量，不能正确表达1＜X＜5的逻辑表达式是（）。

A.1<X<5

B.X=2 or X=3 or X=4

C.1<X And X<5

D.Not （X<=1） And Not （X>=5）