看看第三种用法 是此题的解
现将before用法归纳如下：
1．表示“在……之前”.说明两个时间或两个事件之间的先后关系.
1)They had got everything ready before I arrived．在我到达之前他们已经把一切都准备好了.
2)She didn’t understand me before I explained it to’her．在我向她解释之前,她不理解我的意思.
3)The train had left before I arrived at the station．在我到达车站之前火车已开走了.
2．表示“……才…… ”,强调从句的谓语动词所表达的时间、距离很长或花费的力量比较大.
1)The workers worked long hours for two weeks before everything returned to normal．工人们长时间地工作了两周,一切才恢复
正常.
2)Thebig fire lasted four hours before the firemen brought it under contro1．大火持续了四个小时,消防队员才把它控制住.
3) We waited a long time before the train arrived．我们等了很长时间火车才到.
3．表示“还未来得及……就……”,强调主句谓语动词所表达的时间、距离很短或花费的精力比较小.
1)Before I could figure out what had happened,he forced me into the car．我还不知道发生了什么,他就强行把我推进了汽车.
2)He jumped into the water before I could stop him．我还没有来得及阻止他,他就跳进了水里.
3)Her father died before she was born．她尚未出世父亲就去世了.
4．表示“趁着……”.
1)We can set off early before it gets hot．我们可以趁着天不热早点出发.
2)You’d better write the phrases down before you forget them．趁着你还没有忘记,赶紧把这些词组写下来.
3)Please put them away before they are missing．趁着他们还没有丢,把它们收好吧.
5．表示“一……就”、“刚刚……就”.与hardly．scarcely连用o
1)He hadhardly gone to bed before(=when)the door bell rang．他刚刚睡下,门铃就响了.
2．She had scarcely got off the train before(=when)her daughter ran towards her．她刚一下车,女儿就跑了过来.
6．表示“不知不觉多少时间已经过去了”.
1)He was so absorbed in his work that four hours had passed before he knew it．他如此专注于工作,不知不觉四个小时就过去了.
2)Time passed quickly and three months went by before he knew it．时间飞快地流逝,他没感觉到三个月已过去了.
7．表示“宁可.宁愿”,相当于rather than.
1)I’d die before I apologized to"them．我宁死也不向他们道歉.
2)1 would be poor before I got money in this way．我宁愿穷也不愿用这种方式挣钱.
8．before常用于句型“it was……before……”“
过了(多长时间)才…… ”,“it will be……before…… ”
“要用(多长时间)才……”.“it wasn’t……before……”
“没过(多长时间)就……”.“it won’t be……before……”“用不了(多长时间)就会……”.
1)It was long before he came to help me．过了很久他才来帮我.
2)It wash’t long before the fire was put out．不久火就给扑灭了.
3)It will be another five days before we finish this task．还要再过五天我们才能完成任务.
4)It won’t be a long time before someone comes to see you．不久就会有人来看你.