open什么时候用被动语态？
open没有被动语态。open在使用的时候一般句子的主语通常是指物，不及物动词的主动形态表被动意义，主要表达主语内在的“品质”或者“性能”，例句：This door doesn't open well.（这扇门不好打开）。
一般说来，当 open, close, shut, lock, move 等用作不及物动词且表示主语的某种属性时，通常用主动形式表示被动意义。如：
The door won’t shut. 这门关不上。
The supermarket doors shut automatically. 超市的门是自动关的
open做及物动词时都可以用做被动语态。
例句
1.
She motioned for the locked front doors to be opened
她示意把锁着的前门打开。
2.
The road will be opened again in a few hours after police have cleared it.
待警察清理完以后，道路在几小时内就会重新开放。
3.
The border, effectively closed since 1981, will be opened as of January the 1st
实质上从1981年就已关闭的边境将于1月1日开放。
1.当open是及物动词后面接宾语的情况下都可以用做被动语态。
2.例句He often opens the door in the morning.被动语态就是The door is often opened by him in the morning.
3.We opened the window yesterday.变成被动语态就是The window was opened by us yesterday.
