John has finished his homework .John's homework has been finished by him.we must do something to protect the environment.Something must be done to protect the environment.被動(dòng)語態(tài) 要怎么去理解啊先說 主動(dòng)語態(tài)，就是誰 做了什么那么相對(duì)的，被動(dòng)語態(tài)，就是 什么被誰做了那有什么格式的么？動(dòng)詞的形式分三種現(xiàn)在時(shí)，過去時(shí)，過去分詞被動(dòng)語態(tài)中，要用動(dòng)詞的過去分詞的形式