下列物质属于纯净物的是（） A．空气 B．干冰 C．矿_爱下问搜题

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问题选择题

下列物质属于纯净物的是（　　）

A．空气

B．干冰

C．矿泉水

D．食盐水

答案

A、空气中含有氧气、氮气、二氧化碳等多种物质，是混合物；

B、干冰是固态二氧化碳，只有一种物质，是纯净物；

C、矿泉水中含有水和其它矿物质，是混合物；

D、食盐水是由食盐和水组成的混合物．

故选B

阅读理解

阅读理解。

Dear Cindy,
     How's going with you? For me it's terrible. Three are too many rules in our school. It isn't fair. I have
to get up at five forty every morning.  I can't be late for running, I have to run at six thirty. I have to
practice English and Chinese every day. In the evening I can't watch TV or hang out with friends because
I have to do my homework. I have to go to bed before ten o'clock. What's more? We can't listen to
music or eat in the classroom. We even can't wear hats or have long hair. We have to wear school
uniforms every day. On weekends, I still have to stay at school on Saturday. Because I have to learn
science and math. Do you have lots of rules in your school? Are they fair?
                                                                                                                             Your friend,
                                                                                                                                Alex

1. Who is the letter from?

A. Cindy.
B. Alex.
C. Cindy's teacher.
D. Alex's teacher.

2. What time does Alex have to get up?

A. Five forty.
B. Six forty.
C. Five o'clock.
D. Six thirty.

3. What does Alex have to practice every day?

A. English.
B. Chinese.
C. French.
D. A and B.

4. Why does he stay at school on Saturday?

A. To hang out friends.
B. To learn math and science.
C. To listen to music.
D. To play soccer.

5. Why is Alex not so happy?

A. Because he can't wear school uniforms.
B. Because he has nothing to do at school.
C. Because there are so many rules in his school.
D. Because there are so many rules in his house.

选择题

The young couple reached their house in the evening and found that someone _____ into the house

during the day. [ ]

A. broke

B. had broken

C. has broken

D. was breaking