根据句意和首字母完成下列句子。

1. Sorry, I can't u _____ you.

2. He has t_____ me a lot about you.

3. I have a friend who s_____ English.

4. Yesterday my cousin p_____ me.

5. Please repeat. I can't f_____ you.

6. My grandma t_____ me a good story last night.

7. He often e_____ me to do everything.

8. May I s_____ to Jenny?

9. Pardon? Please speak more s_____.

10. I w_____ love to talk with her.

在关系代数的连接操作中，哪一个操作需要取消重复列？（）

A.等值连接

B.自然连接

C.连接

D.笛卡儿积