问题 选择题

已知Ag2SO4的Ksp为2.0×10-5,将适量Ag2SO4固体溶于100 mL水中至刚好饱和,该过程中Ag+和SO42-浓度随时间变化关系如图[饱和Ag2SO4溶液中c(Ag+)=0.034 mol·L-1]。若t1时刻在上述体系中加入100 mL 0.020 mol·L-1 Na2SO4溶液,下列示意图中,能正确表示t1时刻后Ag+和SO42-浓度随时间变化关系的是

[ ]

A.

B.

C.

D.

答案

答案:B

阅读理解

Reading comprehension.

     Have you heard about "Survival (生存) Holidays" ? "Survival Holidays" is for children to go into the lonely

place for exciting activities. Now about 1,100 companies are allowed to take children into the great outdoors

without their parents.

     The reason why people like "Survival Holidays" is that they think being close to nature is good for children.

Many children in big cities spend all time watching TV and playing computer games. "Survival Holidays" gives

them an important change.

     Is "Survival Holidays" a wonderful idea? Maybe it is. Children need more free time to play. They need to be

left on their own, without adults disturbing (打扰) them. Parents care too much about their children. They like

to see the children being busy with activities that are controlled by adults, but children don't know what to do

when they are in danger. Even something like crossing a small river seems to be a hard challenge. Children are

not comfortable with danger. Even small danger like getting their feet wet or falling down seems very terrible

to them.

     Many people think the survival activities are good for children. Even years later, they will still remember

what they have learned. Some have learned to stay calm in different times. Some have learned how to keep safe.

Others have learned how to work in a team. All these skills will help them a lot in their lives.

Answer the following questions according to what you read.

1. Is "Survival Holidays" for children or parents?

    _____________________________________________________________

2. Why do people like "Survival Holidays"?

    _____________________________________________________________

3. What do the children in big cities usually do? 

    _____________________________________________________________

4. How do children feel when they are in danger?

    _____________________________________________________________

5. What can children learn in the survival activities? 

    _____________________________________________________________

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