Ⅰ. ago adv. “……以前”指從此刻起，若干時(shí)間以前，通常與過(guò)去連用。如：

① It happened two days ago.這件事發(fā)生在兩天以前。

② I met him a few minutes ago.我在幾分鐘以前碰到他。

Ⅱ. before adv, prep & conj “……以前”指從那時(shí)起若干時(shí)間以前。通常與完成時(shí)、過(guò)去時(shí)等連用。還可用作前置詞或連接詞表時(shí)間，而ago 則不能這樣用。

① He said that he had seen her two days before.他說(shuō)他兩天前見(jiàn)到過(guò)她。(表從她說(shuō)話那時(shí)起兩天前)

② I had been fine the day before.(那天)前一天的天氣很好。

③ I’ve seen that film before.

④ I never met him before.

本文來(lái)自：逍遙右腦記憶 http://m.yy-art.cn/gaozhong/683800.html

相關(guān)閱讀：英語(yǔ)短語(yǔ)學(xué)習(xí)：開(kāi)綠燈