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问题 选择题

某同学用显微镜观察洋葱表皮细胞临时装片时观察到图1所示图象，然后换用高倍镜后视野的亮度发生了如图2所示的变化，应如何调节才会更加清楚？

（　　）

①选用小光圈       

②选用大光圈 

③选用平面镜 

④选用凹面镜．

A．①③

B．①④

C．②③

D．②④

答案

换用高倍镜后视野的亮度发生了如图2所示的变化，说明视野变暗了，应把显微镜的视野调亮选用大光圈、凹面镜调节

A、①③选用小光圈、平面镜调节，显微镜的视野最暗，故该选项不符合题意；

B、①④选用小光圈、凹面镜 视野亮度不是最亮，故该选项不符合题意；

C、②③选用大光圈、平面镜，视野亮度不是最亮，故该选项不符合题意；

D、②④选用大光圈、凹面镜视野亮度最亮，故该选项符合题意；

故选D．

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We all need a healthy environment, but we p 小题1:waste every day and it does harm to our environment. Though we are young, we can still do something to help. In fact, even the s 小题2:everyday activities can make a real d 小题3:to the environment. Here are some ideas for you to live a green life.

Remember these three words: reduce, reuse and recycle.

Reduce means “don't waste things” .This s 小题4: money and reduces pollution and waste going into the environment. Before we buy something new, think if it is really n 小题5: or maybe the old one will be just as good! When we do buy things, choose local products if possible, and try not to buy too many things from a 小题6:.

Reuse means “use again”. Use things for as long as possible. When we buy things, make sure that they last a long time. We should take care of them so that they will last, and we should r 小题7: them if we can instead of throwing them away and buying new ones. Don't use a paper cup or a paper bag. It’s better to use a china cup and a lunch box b 小题8:you can use them again.

Recycle means “change things into something else”. A 小题9: it takes energy to change something into something else, it’s better than throwing things away or b 小题10:them. Find out what can be recycled in your neighbourhood and take part in recycling programmes. We should also buy products made from recycled materials, such as recycled paper, to help save trees.
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计算题
用简便方法计算下面各题．
（1）8.35×101﹣8.35     （2）（3.4×0.8+9.2×3.4）÷34÷0.05
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