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Mr. Jones has worked here since he was twenty-five.
2. for作介词，后接一段时间，表示一个动作或一种状态已经持续了多长时间。如：
I have studied here for three years.
She has been away for five days.
注意：
1.?对since和?for引导的时间状语提问时, 常用how long。如：
Jane has learned to play the piano
since two years ago.? (对划线部分提问)
How long has Jane learned to play the piano?
2.?在现在完成时中，含有for和since的句子可以相互转换。如：
They have lived here for five years.
=They have lived here since five years ago.
3.?在现在完成时中，表示短暂意义的动词(如come和see)在肯定句和一般疑问句中不能和表示一段时间的时间状语连用，但在否定句中是可以的。如：
Mike has come to London for three weeks. (×)
They haven’t seen each other for ages. (√)
短暂性(短语)动词与延续性(短语)动词
和与表示状态的短语之间的转化
1.?有些短暂性(短语)动词可转化为相应的延续性(短语)动词。常见的有：
become?→?be borrow?→?keep?
buy?→?have / own
catch a cold?→?have a cold
come?→?stay put on?→?wear
go to sleep?→?sleep? move to?→?live in
2.?有些短暂性(短语)动词可转化为表示状态的短语。常见的有：
leave?→?be away
begin / start?→?be on
die?→?be dead finish?→?be over
join?→?be in / be a member of
fall asleep?→?be asleep
marry?→?be married?