问题补充：
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：句意：你最好在有疑问的地方做个标记。考查地点状语从句。所以用where引导。如果加上at可以改成 at a/the place where ，where 在这儿引导的定语从句。place 做了at的宾语。
