Passive voice
Only the sentences with transitive verbs (verbs with objects) can be changed to passive sentences

-Simple present tense

S= subject
O= object
v= verb
> Active
Pattern : S + V1 S/ES + 0
S + V1 + O
>Passive : Pattern : O + is/am/are + V3 (By....)

- simple past tense
> Active
Pattern : S + v2 + O
>Passive
Pattern : O + was/were + V3 (by....)

-Present continues
> Active
Pattern : S + is/am/are + V1ing + O
> Passive
Pattern : O + has/have + been + v3 (by....)

- Present perfect tense
>Active
Pattern : S + has/have + v3 + o
> Passive
Pattern : O + has/have + been + v3 (by....)
- Present future "be going to "
> Active
Pattern : S + is/am/are + going to + v1 + O
> Passive
Pattern : O + is/am/are + going to be + v3 (by...)

- Sentences with modals (can,may)
> Active : s + modals + v1 + o

> Passive
Pattern : O+MODALS+BE+V3 (BY....)

IN QUESTIONS
WHAT DO YOU LOOK?
CHANGED TO PASSIVE :WHAT IS LOOKED BY YOU?
DID THEY BUY A CAR?
ANSWER : WAS A CAR BOUGHT BY THEM

ONLY THIS I CAN TELL YOU. IF YOU HAVE MORE, JUST WRITE IT



http://www.indogamers.com/f258/all_about_grammar-12501/