Before ______ white,the door should be cleaned thoroughly.A.
2个回答

A.before 引导的应该是时间状语从句,完整的句子应该是Before it is painted white,the door should be cleaned thoroughly.因为从句和主句的主语指的是同一事物,就是the door,而从句的动词又是be动词,所以省略从句的主语和be动词,就是省略it is,最后就剩下Before painted white,the door should be cleaned thoroughly.因此选A.