几个英语单句改错.请说明改错方法及理由,

几个英语单句改错.请说明改错方法及理由,
1 One that fears nothing is certainly brave.
2 He lives in a house which windows face south.
3 There are many young men that are against the plan.
4 You should hand in all which you have.
5 The girl who often help mo with my English is him.
6 He has three sons,two of them are music lovers.
5句中mo为me,him为her
3、4句什么理由啊?
6句,当两个单句理解可以吗?