空间三个平面如果每两个都相交，那么它们的交线有 A．1条

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问题选择题

空间三个平面如果每两个都相交，那么它们的交线有

A．1条

B．2条

C．3条

D．1条或3条

答案

答案：D

解：比如墙角，此时交线有3条，或者三个平面过一条交线，比如我们的书，可以以书边为交线，出发的平面有无数个，就可以相较于一条交线，因此选D

填空题

用适当的介词填空。

1.—Where was your sister born? —She was born ______ Shanghai.

2. The date ______ her grandmother's birthday is July 18.

3. Look! There are a lot of birds ______ that tree.

4. How many months are there ______ a year?

5. Kate's kite is ______ that tree. She can't get it down.

6. We have a sports meeting every year ______ school.

7. The shoes ______ the bed are my parents'.

8. Welcome ______ our sports club.

9. Can you take the notebook ______ the reading room for Tom?

10. Her brother was born ______ December 24.

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