. The book is blue is mine.A. the cover of whichB. whose coverC. of which the coverD. a

问题补充：

. The book, is blue, is mine.

A. the cover of which

B. whose cover

C. of which the cover

D. all the above

答案：

A. the cover of which

B. whose cover

C. of which the cover

(答案→)D. all the above

解析：考查定语从句，先行词是the book，定语从句缺少cover的定语，用whose cover引导，=of which the cover也等于the cover of which，所以选D，句意是：封面是蓝色的书是我的。选D。