各时态的被动
时态体现在 be 上，过去分词永远不变。
is done／was done／will be done／has been done
要点
- 被动语态的时态全部由 be 来体现。
- 一般现在时：am / is / are + done。
- 一般过去时：was / were + done；一般将来时：will be + done。
- 现在完成时：have / has been + done。
- 进行时的被动要加 being：The road is being repaired now.（正在被修）—— 但完成进行那一式（has been being done）英语里几乎不用，宁可换成人称作主语的主动句。
- 过去完成时的被动是 had been done：The room had been cleaned before we arrived. —— 这一格要有一个更早的过去动作作参照（见「过去完成时」）。
- "将来被…"除了 will be done，还能说 be going to be done：The bridge is going to be pulled down. —— 这一式带"已经定下"的味道，与「一般将来时」同一条分界。
例句
It is made of wood.
它是木头做的。（一般现在时）
Paper was invented in China.
纸是中国发明的。（一般过去时）
The treaty was signed by both countries.
条约由两国签署。（一般过去时）
Many treasures have been stolen.
许多珍宝被盗。（现在完成时）
A new bridge is being built over the river.
河上正在架一座新桥。
The film had been shown twice before I got there.
我到那儿之前那片子已经放过两遍了。
易错提示
- 过去分词永远不变，变的是前面的 be。
- 含情态动词的被动：must be done、can be done。
- 情态那一头的式子也只动 be 那一段：must be done 与 must have been done 里的 done 一模一样 —— 细则在「含情态动词的被动」那条。