(改写) Who ate my bread? （改为被动语态）By whom _ my bread _?

Who ate my bread?（改为被动语态）

根据要求改写句子，每空一词。
1. They had an English party last Sunday. (改为否定句)
They_______________an English party last Sunday.
2. He thinks the fastest way to travel is by plane. (对画线部分提问)
 _______does he think_______ the fastest way to travel?
3. Who ate my bread? (改为被动语态)
By whom_______ my bread_______?
4. The girl with a flower in her hand is my sister,  (改为含有定语从句的复合句)
The girl _______________a flower in her hand is my sister.
5.1 don\'t know what I should do with the letter. (改为简单句)
I don\'t know what _______________with the letter.