Công thức

CĐ: S + V + O...

-->BĐ : O + be + V ( ed/ c3 ) + ( by S ) ...

Cụ thể : 

1, It should be sent to mother right now

2, His debt must be paid before the first of the month

3, His debt has to be paid before December

4, An excursion may be organized by the Browns next week

5, His work has be completed today

`1.` It should be sent to mother right now

`2.` His debt must be paid before the first of the month

`3.` His debt has to be paid before December

`4.` An excursion may be organized next week.

`5.` Bill's work has to be completed today

`@` Kiến thức câu bị động :

`-` S + should be + P2 ( by O )

`-` S + must be + P2 ( by O )

`-` S + have/has to be + P2 ( by O )

`-` S + may be + P2 ( by O )