1\The butter is kept by us here.
2\The window is broken by them.
3\A meeting will be held by us.
4\Some cakes are going to be made by them.
5\The bike is being ment by them.
6\A tiger has been seen by me.
7\A tiger had been seen by me.
8\A box was being carried by them.
9\The flowers should be watered by us.
(如有疑问可以随时讨论)