The infinitive passive voice is used after modal verbs and other most verbs normally followed by an infinitive.
- You have to be tested on your English grammar.
- Sheela might be promoted next year.
There are two basic patterns we use for passive modals.
1. modal + be + past participle
Active modal: can see
Passive modal: can be seen
Example: The painting Monalisa can be seen in the Louvre.
2. modal + have been + past participle
Active modal: could have done
Passive modal: could have been done
Example: It could have been done by Ammu.