1.先找出谓语动词；
2.再找出谓语动词后的宾语；
3.把宾语用作被动语态中的主语；
4.注意人称、时态和数的变化.
例：1.Bruce writes a letter every week.→A letter is written by Bruce every week.
2.Li Lei mended the broken bike this morning.→The broken bike was mended by Li Lei this morning.
3.He has written two novels so far.→Two novels have been written by him so far.
4.They will plant ten trees tomorrow.→Ten trees will be planted by them tomorrow.
5.Lucy is writing a letter now.→A letter is being written by Lucy now.
6.You must lock the door when you leave.→the door must be locked when you leave.
