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问题 选择题

下列物质属于纯净物的是（　　）

A．葡萄糖

B．可乐

C．生铁

D．食醋

答案

可乐是溶液、生铁是铁的合金、食醋是醋酸的溶液，三者都是混合物，只有葡萄糖是纯净物中的有机物．

故选A

阅读理解

Hello, my name is Lisa. There are twelve months in a year. Among(在…之间)  them, I like May, because my birthday is on May 21st. On that day, my parents have a birthday party for me. My cousin Beth’s birthday is in May, too.  I like her, and she likes me. We are good friends. But   she is only 3 years old. She is the daughter of my uncle and aunt. She likes June very much because  Children’s Day is in it. My father likes October very much because every year, at that time, there are lots of ball games and he likes watching them. My mother likes September and October because Mid-autumn Day (中秋节) is in these two months.

小题1:How many months are there in a year?

小题2:Why does Lisa like May?

小题3:Is Beth Lisa’s sister?

小题4:What does Lisa’s father like doing?

小题5:Which months does Lisa’s mother like?
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实验题

小华测滑轮组机械效率的实验过程如图所示。小华在匀速拉动弹簧测力计时，弹簧测力计的示数如图丁所示。

（1）请你认真观察上面的实验数据，计算出滑轮组做的有用功是 ___________ J，做的总功是 ___________ J，机械效率是 ___________ %。

（2）仅增加提升钩码的个数，滑轮组的机械效率 ___________ （填“增大”、“不变”或“减小”）。

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