by-the-time-用法PPT课件
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By the time 用法详解•by the time意为“到……时候(为止)”,是一个介词短语,在句中经常起连词作用,引导时间状语从句。
它的主要用法如下:• 1. 如果从句中的谓语动词是一般过去时,那么主句中的谓语动词通常用过去完成时,表示“截止到从句动作发生时,主句动作已经完成,即过去的过去”。
例如:By the time he returned home,the rain had stopped.• By the time I got to the station,the train had already gone。
• 2. 如果从句中的谓语动词为一般现在时/或现在完成时(表示将来),那么主句中的谓语动词常为将来完成时,表示“截止到将来某一时间为止,主句动作将已经完成”。
By the time you get back,I shall have finished the work.• By the time I graduate next year, I will have lived here for 5 years. • By the time of next term , we will have learned 3000 words.• 3. 如果主句动作不强调已经完成,只是说明某个时候的状况,(主句是be的系表形式或者是表示像know, find, believe等表示认知的持续性动词,则往往用一般时态,不用完成时态。
)此时主句不用完成时,而应根据实际需要选用适当的时态,此时by the time相当于when。
例如:• He was out of breath by the time he reached the top.By the time the bus came,so many people were waiting that it was a free fight to get on it. 公共汽车来的时候,等车的人很多,成了一场挤车的混战。