$\text{1.}$ This tree is watered everyday .

$\text{2.}$ All the flights were cancelled because of fog .

$\text{3.}$ This road has been repaired .

$\text{4.}$ These postcards are sent to us by our friends .

$\text{5.}$ The house was broken into .

$\text{6.}$ He isn't taken care by his mother .

$\text{7.}$ The dinner is being prepared in the kitchen by her mother .

$\text{8.}$ The English grammar have been explained by our teachers .

$\text{9.}$ His parents will be visited by Tom next month .

$\text{10.}$ The homework is being done . 

$\text{11.}$ A story is going to be told us. 

→ Quá Khứ Đơn : S + was/were + Vpp + ( by O ) 

→ Hiện Tại Đơn : S + is/am/are + Vpp + ( by O ) 

→ Hiện Tại Tiếp Diễn : S + is/am/are + being + Vpp + ( by O ) 

→ Tương Lai Đơn : S + will + be + Vpp + ( by O ) 

→ Tương Lai Gần : S + is/am/are + going to + be + Vpp + ( by O ) 

→ Hiện Tại Hoàn Thành : S + has/have + Vpp + ( by O ) 

→ Đối với các chủ ngữ I,we,you,they,he,she,it, somebody , someone , people , .... thì ko nhất thiết cần by O 

→ Các trường hợp dùng by O : VD : by her mother , by Lan , by my sister , ...