many rivers have been made ___these years

问题描述:

many rivers have been made ___these years
A.dirty B.to dirty C .be dirty D.to be dirty

A 这些年来,很多河里的水都被污染了.  为什么不是D,能讲一下区别或原因吗,谢谢be made + 形容词这是固定搭配,记住才能会。