请英语好的同学帮忙教我一下这几道关于定语从句的题目,

改错题：
He has two sons,each of them lookks like him.
改成定语从句：
He has two sons,each of whom lookks like him.
理由：
两句话之间不能用逗号来连接,必须用关系词和连词来连接.因此把each of them改成了each of whom
Please pass me the book that cover is red.
Please pass me the book whose cover is red.
表示所属关系的关系代词不能用that,而要用whose;whose表示先行词the book和cover之间的所属关系“是这本书的封面”
whose的先行词可以是“人”,也可以是“物”.
填空题：
He paid the boy 10 dollars for washing ten windows,most(of which )hadn’t been cleaned for at least a year.
关系代词which的先行词是ten windows.
most of which=most of the ten windows
of是介词,在介词后面关系代词不能用that,表示“人”用whom;表示“事”或“物”用which.
在这里表示“物”,用which