The sentence(s) in Passive Voice

Варианты ответа

1. A.How old are those houses?
2. B.Butter is made of milk.верно
3. C.The office is being cleaned at the moment.верно
4. D.I've never seen these flowers before.
5. E.When was telephone invented?верно
6. F.I'm going to take an umbrella with me.