That art center is used to be a factory, millions of cars were made．
A. what; which
B. where; where
C. what; where
D. where; which
网友回答
A. what; which
B. where; where
(答案→)C. what; where
D. where; which
解析：考查定语从句和名词性从句。What used to be s factory是一个表语从句，what在句子做主语。where millions of cars were made是定语从句，修饰前面的先行词factory, where在句中做地点状语。