9月1日早上9:27--9:40
Jim hurt his arm playing tennis.
Feeling tired, I went to bed early.
同一主语的两个行为同时发生，其中一个行为常可用-ing 形式来表示。这个短语一般放在主句的后面。
I've just seen Carol. She's in the bar having a drink.
A man ran out of the house shouting.
Do something! Don't just stand there doing nothing!
如果一个行为发生时，另一个行为正在进行，另一方行为可以用-ing 短语来表示：
Jim hurt his arm playing tennis.
Did you cut yourself shaving?
在while 或 when 后面也可以用-ing 结构：
Jim hurt his arm while playing tennis.
Be careful when crossing the road.
如果一个行为发生在另一个行为之前，发生在先的行为用having (done) 表示：
Having found a hotel, we looked for somewhere to have dinner.
Having finished her work, she went home.
after 后也可用-ing 结构：
After finishing her work, she went home.
如果一个短暂行为紧接着另一个短暂行为，第一个行为用-ing 的一般形式，而不用完成式：
Taking a key out of his pocket, he opened the door.
-ing 短语还可以用来解释某事或说明原因，这时它常放在句首:
Feeling tired, I went to bed early.
Being unemployed, he hasn't got much money.
Not having a car, she finds it difficult to get around.
Having already seen the film twice, I didn't want to go to the cinema.
