To form the passive voice, you need the verb to be + past participle of the main verb (-ed for regular verbs and the second column for irregular verbs).
What is... Incorrect.
To form the passive voice, you need the verb to be + past participle of the main verb (-ed for regular verbs and the third column for irregular verbs).
All kinds of things ... (leave) in buses every day.
What is... All kinds of things are left in buses every day.
The passive voice is used if you don't know who performed the action described in the sentence.
What is... Correct.
All the sandwiches ... (eat) at the party last night.
What is.. All the sandwiches were eaten at the party last night.
Children under sixteen ... (not admit).
What is... Children under sixteen aren't admitted.
Oranges were grown here for centuries by Valencians.
What is.. Valencians grew oranges here for centuries.
When the action expressed by the verb is received by the subject, it is passive voice.
What is.. Correct.
Two people ... (killed) in the explosion.
What is... Two people were killed in the explosion.
It is believed that he left the country five months ago.
What is... Passive.
When ... (the hotel rooms/book)? (past)
What is... When were the hotel rooms booked?