题目内容：

They have been friends for 6 years. 改为同义句 They have been friends _______ _______.

优质解答

楼主应该是横线给少了,最常见的变化是：They have been friends for 6 years.= They have been friends (since 6 years ago).或 = They have been friends (as long as 6 years).其中,第一种变化中的since也可以写成...