汽车已经成为现代生活中不可缺少的一部分，汽车多数采用汽油机作为发动机，如图是汽油机工作四个过程的示意图，按照工作循环的顺序将四个冲程进行排列，其中正确的是（   ）

根据课文《和时间赛跑》，写出对句子的理解。

《和时间赛跑》这篇课文中，作者是怎样感到时间流逝的？

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完形填空
      This is my desk, and 1 books are on it. One is yellow and the other(另外的) is blue. You can see a 2 on the desk, too. The clock is red. My pencil case is3 the desk, too. A  pen, an eraser  and a ruler4in it. The pen is black. The5 is yellow, and the ruler is white.
    6 is my pencil? Well, it's under the desk. A baseball is under the7too. But the baseball isn't 8. It's my brother's. Is my computer under the desk, too? No，9isn't. Where is it? I can't10it in the room.

人类只有一个地球，她是我们共同的家园。下列关于环境问题的说法正确的是（）