助动词do可以用来：
1.构成疑问句：
Does he know Chinese?
他懂汉语吗?
How do you like the weather here?
你觉得这里的天气如何?
Did you go by train or by plane?
你是坐火车还是坐飞机去的?
She likes the food，doesn't she?
她喜欢这个菜，对吧?
2.构成否定句：
Don't bother to answer the letter.
不要烦你回信了。
We don't see much of each other.
我们不常见面。
He doesn't care for fish.
他不爱吃鱼。
I didn't know you were here.
我不知道你在这儿。
3.表示前面所说动作，以避免重复：
-Do you work together?
-Yes.we do.
-你们在一起工作吗?
-是的。(我们在一起工作。)
You don't want to be late.Neither does she.
你不想迟到，她也不想迟到。
You're doing better than you did last term
你这学期比上学期表现好。
I said he would fail，and he did.
我说他会失败，他真的失败了。
4.加强语气(起强调作用)：
I do think you’re right.
我确实认为你是对的。
She does feel that way.
她确实有这种感觉。
She did say that.
她确实这样说的。
Do be careful.
千万小心。
5. do在更多情况下用作实意动词，用法很灵活，可表示许多意思，如：
Martin has done an excellent article.
马丁写了一篇精彩的文章。
He has done a portrait of Lilly.
他画了一张丽丽的画像。
We are doing the dishes.
我们在洗碗。
Have you done your teeth?
你刷牙了吗?
He has done Horace into English verse.
他把荷雷斯的作品译成了英文诗。
