and/or/but
当主语一样时，可以省略第二句主语，如：John can read and write.
当动词也一样时，可以第二句的主语和动词都可以省略，如：John likes to eat apples and oranges.
注意省略是可选的，不省句子也是正确。
主语不一样的情况：She and Simon had already gone.
but连接两个句子，表转折，即使两句主语一样也不能省略第二句主语，如
They like to climb, but they didn't go there last week.
both 和 either
both ... and ...用来加强and，如：Some areas are congested with both cars and people.
either ... or ... 用来加强or，如：You can eat either an apple or a pear.
because 和 so
because +句子，强调原因，They like climbing, but they didn't go last week.
because of +名词，其中because of组成一个介词，如She comes because of us.
so +句子，表示因此，如We eat too much food, so we are too full now.
so that 加强so，很多时候so that可以被to + 非限制性动词代替，如：
I get up early so that I can see the sunrise.
I get up early to see the sunrise. // 需要了解的是，to see与前面的动词没有关系，不像是give sth to sb这种固定搭配。
描述事件顺序before、when、after
- before 表示：在..之前
Before he had lunch, he had a nap.
（如果连词打头，则要在句中加逗号）
He took a nap before he had lunch. = He took a nap before having lunch.
- when指：当...的时候
It rained when she was on the way to work.
注意as soon as = immediately when
She gives John a hug as soon as see him.
- after 指：在...之后
He turned off the light after he had breakfast.
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