题目内容：

2 days ago I went to see him,but his neighbour said that he had left four days before,
before 与ago 的区别

优质解答

很简单
ago 用于过去时
before 用于完成时.
ago意思是之前,是一个准确的时间.3days ago,三天之前的那一天.
before不是一个准确的时间.before May,五月之前的那段时间,哪一天不确定.