before與ago用法區(qū)別

1、Before與ago,區(qū)別,before表示從過(guò)去或?qū)?lái)某一時(shí)間算起多少時(shí)間以前，由于與這一時(shí)間狀語(yǔ)連用的行為先發(fā)生在過(guò)去或?qū)?lái)某一時(shí)刻之前，因此往往出現(xiàn)在過(guò)去完成時(shí)態(tài)或?qū)?lái)完成時(shí)態(tài)中。, I called him up last night， but his mother told me he had left for Wuhan two days before. She said that she had married him five years before.,如果不具體表明多少時(shí)間以前，before意為“從前；以前”，表示從現(xiàn)在開始追溯到過(guò)去一段時(shí)間，或者主句的謂語(yǔ)動(dòng)詞表示的是經(jīng)常

2、、反復(fù)發(fā)生的行為，以副詞的形式置于句末，可以用在現(xiàn)在完成時(shí)態(tài)中。 I have never been to Beijing before. Have you ever seen a tiger before? I often go over the lessons that I have learned a few days before.,ago指的是從現(xiàn)在起到過(guò)去時(shí)間的某一點(diǎn)的一段時(shí)間。這個(gè)時(shí)間狀語(yǔ)常與一般過(guò)去時(shí)態(tài)或過(guò)去進(jìn)行時(shí)態(tài)連用。 I graduated from the college twenty years ago I was asked what I was doing a month ago.,按語(yǔ)法規(guī)則，ago只能與一般過(guò)去時(shí)連用，但在since three years ago這類短語(yǔ)中能與現(xiàn)在完成時(shí)態(tài)連用。因?yàn)閠hree years ago構(gòu)成一個(gè)名詞短語(yǔ)，共同作since的賓格，意為自從三年前以來(lái),Practice,I remember seeing you somewhere 2 years _. I have read the novel _. She said she had met Tom 2 years _. She has been there since 3 years _. How long _ did y