把下列主动语态的句子转换成被动语态的形式 英语高手来！谢谢！好的可追加10分！！！

1. young trees must be looked after well by me.
2 your mistakes in your exercises must be corrected by you
3 the letters will be typed by her this afternoon

谢谢 采纳~

Young trees must be looked after well.
Your mistakes in your exercises must be corrected.
The letters will be typed this afternoon by her.

　　1. Young trees must be looked after well by us.
　　2. Your mistakes must be corrected in your exercises.
　　3. The letters will be typed by her this afternoon.

1.We must look after young trees well.
Young trees must be looked after well by you.

2.You must correct your mistakes in your exercises.
Your mistakes in your exercises must be corrected.

3.She will type the letters this afternoon.
The letters will be typed by her this afternoon.