问题补充：
— Where did you buy this beautiful skirt?
— It was in the shop my mother is working.
A. that
B. which
C. where
D. what
答案：
A. that
B. which
(答案→)C. where
D. what
解析：考查强调句和定语从句。该句为强调句的省略形式，完整为It was in the shop where my mother is working that I bought this beautiful skirt.
