people use knives to cut things?变被动语态（下还有）
问题描述：
people use knives to cut things?变被动语态（下还有）
The students don't clean the classroom in the morning.变被动语态
答
1 Are knives used (by people) to cutting
2 The classroom isn't cleaned by the students in the morning .可解释下are和isn't是为什么吗？原句不是do和don't吗？谢谢！被动语动词的结构是：BE +动词的过去分词。