I had to buy these books because I didnt know which one was the best.A. all B. noneC. bo

问题补充：

I had to buy these books because I didn know which one was the best.

A. all

B. none

C. both

D. neither

答案：

(答案→)A. all

B. none

C. both

D. neither

解析：all所有的，指三个及三个以上都；none一个也没有；both两者都；neither两者都不。句意：我不得不全买了这些书，因为我不知道哪一本是最好的。结合语境可知本句中指的是三个或者三个以上，故选A。