before 句型：
(1) before sb can/ could … 某人还没来得及……
例：Before I could get in a word ，he had measured me.
我还没来得及插话，他就给我量好了尺寸
(2) It will be +时间+ before + 还有多长时间……
例：It will be 4 years before he graduates. 他还有四年时间变毕业了。
(3) had done some timebefore(才……)
例：We had sailed four days and four nights before we saw land.
我们航行了四天四夜才见到陆地。
(4)had not done --- before ---不到……就……
例：We hadn’t run a mile before he felt tired.
我们还没走到一英里路就觉得累了。
(5) It was not +一段时间+ before不多久就……
例：It wasn’t two years before he left the country. 还没到两年他们离开了那国家。