Types of sentences in the passive voice.
1. We form positive sentences by putting the verb form on the second place:
SUBJECT + TO BE + PAST PARTICIPLE
The furniture has been delivered.
2. We form questions by putting the verb to be before the subject.
Is your car being serviced?
3. We form negative sentences by putting not after to have or to be.
The office has not been cleaned yet.
4. You should form the passive of infinitives like this:
VERB + TO BE + PAST PARTICIPLE
He wants to be made the right decision.
5. You should form the passive of modal verbs like this:
MODAL VERB + PAST PARTICIPLE
The roof must be repaired as soon as possible.