` 1 ` ; A lot of work was done by him yesterday afternoon 

Bị động QKĐ :

` - ` : S + was / were + VPII + by + O

` DHNB ` : Yesterday afternoon

` 2 `: Meals are often prepared for my family by my mother

Bị động HTĐ :

` - ` : S + be + VPII + by + O

DHNB : Often

` 3 `A letter is being written to her friend at the moment 

Bị động HTTD :

` - ` : S + is / am / are + being + VPII + by + O

DHNB : at the moment

` 4 ` :  Linh's friend is often given a present on the birthday

Bị động HTĐ :

` - ` : S + be + VPII + by + O

DHNB : Often

` 5 ` : My grandparents were visited by me last weekend 

Bị động QKĐ :

` - ` : S + was / were + VPII + by + O

` 6 ` : Their room is being cleaned at present 

Bị động HTTD :

` - ` : S + is / am / are + being + VPII + by + O

DHNB : a present