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问题 选择题

酸雨对生态系统的破坏很大，被称为“空中死神”．酸雨形成的主要原因是（　　）

A．火山爆发

B．农药污染

C．大气中二氧化硫过多

D．二氧化碳污染

答案

酸雨产生的原因主要是因为空气中的二氧化硫、二氧化氮等酸性氧化物过多，这些酸性氧化物结合水形成相应的酸性物质会引起酸雨．火山爆发能引起酸雨，但不是主要原因；农药污染会污染土壤和水，不会引起酸雨；二氧化碳污染会引起温室效应，不会形成酸雨．

故选：C．

单项选择题

风府位于（）。

A、后发际正中直上0.5寸

B、后发际正中直上1寸

C、后发际正中直上2.5寸

D、后发际正中直上5.5寸

E、后发际正中直上7寸
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单项选择题

Everybody dreams. Some people think dreams can tell us about the future. Other people think dreams can tell us about ourselves. It’s like our (11) is talking to us.
Why are dreams (12) strange and hard to understand Some people think our brain uses (13) to talk to us. When we fly, swim, or fall down in our dreams, it has a (14) meaning. Lots of doctors help people (15) their dreams. They find that dreams tell us about our (16) and fears.
These days, many scientists (17) that dreams are very important. During the day, we have many (18) , and our brain receives a lot of information. When we dream, our brain (19) information that is not important, and puts the most important information into our (20) . As we learn more about the brain, we may find answers to our questions about dreams.

Ⅰ. 完形填空

/Close
阅读下列短文，从每小题所给的A、B、C、D四个选项中选出一个最佳选项。

A．special

B．serious

C．similar

D．great
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