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问题 填空题

如果直线l1、l2相交成30°的角，交点为O，P为平面上任意一点，若作点P关于l1的对称点P1是第1次，再作点P1关于l2的对称点P2是第2次，以后继续轮流作关于l1、l2的对称点．那么经过（        ）次后，能回到点P。

答案

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问答题

看图回答问题。

1. Where is the book?

    ___________________________________

2. Where is the cat?

    ___________________________________

3. Where is the cat?

    ___________________________________

4. Where is the box?

    ___________________________________

5. Where is the cat?

    ___________________________________

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单项选择题

Is a gold mine an example of a renewable or non-renewable resource and is the supply curve of gold perfectly elastic or inelastic in theory Type of resource Supply curve（） ①A. Renewable Inelastic ②B. Renewable Elastic ③C. Non-renewable Elastic

A. ①

B. ②

C. ③
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