Rewrite the sentences into the Present Perfect Passive Voice. 1) They have already visited London.
2) I have organized the trip to Great Britain.
3) He has published the book about Great Britain.
4) Children have invited their parents to the party.

London has already been visited by them.The trip to Great Britain has been organisdd by me.The book about Great Britain has been published by him.Children's parents have been invited to the party by them.