I have to buy of the two books because I don’t know which to choose.A. everyB. allC. oneD.

问题补充：

I have to buy of the two books because I don’t know which to choose.

A. every

B. all

C. one

D. both

答案：

A. every

B. all

C. one

(答案→)D. both

解析：both意为：（两者）都。符合题中的the two books.