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

1. A.
   at which
2. B.
   at where
3. C.
   the place
4. D.
   where

 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

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

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