e.g. She is the girl who sings best of all.（关系代词who在从句中作主语）
The comrade with whom I came knows French.（whom在从句中作介词with的宾语）
They rushed over to help the man whose car had broken down. 那人车坏了，大家都跑过去帮。
Please pass me the book whose （of which） cover is green. 请递给我那本绿皮的书。
I'll never forget the days when I worked together with you. 我永远不会忘记与你共事的日子。
