----There are so many girls over there .Which one is your sister?--The one hat is yello

问题补充：

----There are so many girls over there,.Which one is your sister?

----The one hat is yellow.

A. who

B. whose

C. that

D. which

答案：

A. who

(答案→)B. whose

C. that

D. which

解析：句意：那边有如此多的女孩，哪个是你的妹妹？带黄色帽子的那个人。whose在从句中作定语，结合句意，故选B .