?一、規(guī)則：在通常情況下 ago 只與過去時連用，而不與現(xiàn)在完成時連用。因為ago指的是多久以前的過去時間，而現(xiàn)在完成時表示的動作雖然發(fā)生在過去，但它強調(diào)的是與現(xiàn)在的聯(lián)系或?qū)ΜF(xiàn)在的影響，因此兩者不能用在一起。如：我兩個月前見過他。誤：I have seen him two months ago. 正：I saw him two months ago.

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二、特例：但是，有時為了行文的需要或使句子生動，ago可用于類似以下這樣的句子：I had thought that he had died at least 20 years ago. 我原以為他至少在< ago. years 20 least at died had he that>20年前就已經(jīng)去世了。