根据汉语或首字母提示完成句子.

1. Bill Gates gives a lot of money to________(慈善机构)every year.

2. He is wearing a black shirt and a pink_______(领带)．

3. Money was always a big ________ (烦恼) for us.

4. I will get n _________ when I answer the teacher's question.

5. Tom received many p ________ in his tenth birthday.

6. I get p ________. They look terrible. What should I do?

7. Are you n_________ before big exams?

8. I'm r ___________ shy and I just don't enjoy parties.

简述D-4型电铲回转拉闸的工作原理。