怎么把句子改成被动语态？

Question

请把下列各句改成被动语态.
1. I bought a pen.
2. I ate a meal.
3. She got a bike.
3. We saw a big bird.
4. We cut down the tree.
5. Mike drew a picture.
6. My father painted the wall.
7. He ran the the company.
8. She took away the bag.
9. I checked the email.
10. He cleaned the room.

Answer 1

把一个句子改成被动语态，第一步把宾语做主语，保留原句时态，按被动语态公式：be＋过去分词。
1, A pen was bought by me.
2, A meal was eaten by me.
3, A bike was got by her.
4, The tree was cut down by us.
5, A picture was drawn by Mike.
6, The wall was painted by my father.
7, The company was run by him.
8, The bag was taken away by her.
9, The email was checked by me.
10, The room was cleaned by him.

Answer 2

their classroom are often cleaned by them after school.
keys were often used by us for locking doors.

主动句是指该句主语是谓语所表示的动作行为的发出者的句子。被动句则是指该句主语是谓语所表示的动作行为的承受者的句子。
主动句和被动句互相转换的要点是主语和宾语的转换：主动句变被动句时，将主动句的宾语变为被动句的主语，主动句原来的主语与“被”构成介宾短语作被动句的状语；被动句变主动句则恰好相反。