—Where did you e across our Chinese teacher?
—It was in the supermarket I purchased mooncakes.
A. that
B. which
C. where
D. when
网友回答
A. that
B. which
(答案→)C. where
D. when
解析：C 考察定语从句和强调句型。本句的答句部分是强调句的省略形式。补充完整是：It was in the supermarket I purchased mooncakes that I came across our Chinese teacher。被强调部分包括一个定语从句，先行词是supermarket，在定语从句中做地点状语。故C正确。