下列情况中的物体可以看作质点的是（   ）

阅读理解。

    Amy and Sarah are good friends. They are from America. They like winter in America because there are many activities in winter. They can make a snowman,go fishing and go skiing with many friends. There are two festivals (节目) in winter. They're Christmas Day and Thanksgiving. Amy and Sarah are very happy. But they're in Beijing now. They like winter in Beijing, too. Because It's beautiful. It's windy and cold. They're going to visit the Great Wall, so they're very happy.

将一矩形玻璃砖从中间斜切后，向左右沿水平直线拉开一小段距离，如图所示，一条光从左侧面垂直射入，画出这条光线从右侧玻璃砖射出的折射光路图（保留作图痕迹）．

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下列句子没有语病的一项是(   )

下列有关人体血液和血液循环的叙述错误的是（　　）