很高兴能够在这里回答你的问题,
1.The emperor invented tea a long time ago.
Tea was invented a long time ago by the emperor .
2.We found some jewels in a box.
Some jewels were found in a box by us.
3.The teacher keeps the pupils at school for a revision.
The pupils are kept at school for a revision by the teacher.
4You must finish the article before Friday.
The article must be finishe before Friday by you.
5They will paint the house again next year.
The house will be painted again next year by them.