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问题 选择题

将80g20%的NaCl溶液变成10%，下列方法正确的是（   ）

A．加入80g水

B．加入16gNaCl

C．倒掉40g

D．加入40g5%的NaCl溶液

答案

答案：A

题目分析：A 加入80g水后溶液的质量分数可以变为一半，变为10%；B加入16gNaCl质量分数变为；C倒掉40g水后溶质的质量分数不变；D加入40g5%的NaCl溶液溶质的质量分数为。

点评：溶液的稀释属于基本的化学知识点，较为简单，中考中常在选择题和填空题中出现，平时应注意对细小知识点的识记。

阅读理解

阅读理解。

      My name is Peter. I'm fourteen. There are four people in my family. They are my father, my mother, my

brother and I. My mother and father are doctors. My brother and I are at school.

      We have a big house. There is a tall tree in front of the house. My father and mother often sit under the tree

and read books. We sometimes play there.

      My brother and I are in the same school. We like our school very much.

1. How many people are there in Peter's family?[ ]

A. Two.

B. Three.

C. Four.

D. Five.

2. Is there a tree behind their house? [ ]

A. Yes, there is.

B. No, there isn't.

C. Sorry, I don't know.

D. All right.

3. Peter and his brother are _______. [ ]

A. in the school

B. the same age

C. not in the same school

D. teachers

4. What's Peter's parents' (父母的) job? [ ]

A. They are teachers.

B. They are doctors.

C. They are workers.

D. They are students.

5. Peter's parents often _______ under the tree. [ ]

A. walk

B. work

C. read

D. clean
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单项选择题

1.44MB软盘的所有磁道中，在最外圈的是( )道，它是软盘中最重要的磁道。

A．0

B．1

C．79

D．80
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