When you read the book you’d better make a mark you have any questions.A. at whichB. at

问题补充：

When you read the book, you’d better make a mark you have any questions.

A. at which

B. at where

C. the place

D. where

答案：

A. at which

B. at where

C. the place

(答案→)D. where

解析：考查地点状语从句。所以用where引导。句意；当你看书时，最好在你有问题的地方做上标记。