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 subject in between the two parts of the verb form.
TO BE + SUBJECT + PAST PARTICIPLE
Is your car being serviced?
3. We form negative sentences by negating the form of "to be".
SUBJECT + TO BE (negation!) + PAST PARTICIPLE
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. We construct a sentence in the passive voice including modal verbs like this:
MODAL VERB + BE + PAST PARTICIPLE
The roof must be repaired as soon as possible.