1.看从句 that you want,你想要的书,书是宾语,你是主语.例如,我吃苹果,苹果是宾语,我是主语
2,看从句,whose cover is yellow,它的（the book‘s）封面是黄色的.它的封面,做主语,is 系动词,yellow,表语.
看这句,The boy is Tom whose brother is Mike.
Whose （指代Tom）的兄弟是mike.这里Tom 是主语