chuyển các câu trên ra thể bị động giúp mih vs

`@Huyyy`

`@`  Bị động của các thì liên quan `:`

`-` Hiện tại đơn `:` S `+` am/is/are `+` Ved/3 `.`

`-` Quá khứ đơn `:` S `+` was/were `+` Ved/3 `.`

`-` Hiện tại hoàn thành `:` S `+` have/has `+` been `+` Ved/3 `.` 

`------------`

`21.` His story isn't believed `.`

`22.` The dam may be broken by a sudden increase in water pressure `.`

`23.` Books borrowed from the library must be taken good care `.`

`24.` I was told about it by a man I know `.`

`25.` He can never be found at home for he is always on the move `.`

`26.` Milk is used for making butter and cheese `.`

`27.` Human life has completely been changed by Science and Technology `.`

`28.` My Cold used to be visited by John at weekends `.`

`29.` The river bank is covered by weeds `.`

`30.` The room was filled with smoke `.`