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问题 选择题

正方体ABCD-A1B1C1D1各面上的对角线与正方体的对角线ＡＣ１垂直的条数是    （　　）

A．４条

B．６条

C．１０条

D．１２条

答案

答案：B

本题考查线线垂直，线面垂直的判定和性质，空间线线，线面关系的转化及空间想象能力.

 

连接，因为是正方形，所以又

，，所以

同理故选B

完形填空

根据短文内容及首字母提示，填写所缺单词

In modern society the competition is so enough, but team spirit can lead us to success. Team spirit means the willingness of people to work t小题1: and help each other as part of a team. With this spirit, people try hard to make their team the best of all. E小题2:  has experienced team spirit one way or another, whether they were part of a team or saw a group of people cheer for their f小题3:  player.

There are different kinds of team spirit. One kind is the connection between a team of people because their efforts and cooperation(合作) are n小题4: in reaching a particular goal. Another kind is when a group of people support a person or a team. Another is people’s natural love for and pride in their country, w小题5:  all the people of the nation cheer for their country in competitions.

Team spirit creates various good effects. It creates friendship and trust(信任) between people who may not get along well when they don’t have such team spirit. There may also be bad effects. Too great team spirit may c 小题6:   fights or quarrels with other team members.

Some people don’t u小题7:  team spirit properly. They think team spirit means having to become a m 小题8: of a team or a fan club. In fact, team spirit can be built anywhere---between friends, coworkers or e 小题9:  between two people sitting next to each other. You don’t h小题10: to wear the team spirit clothes. Anyone can show team spirit just by showing support for the goal.

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问答题

自由基聚合主要分为几步？每步有什么特点？
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