Chan’s restaurant on Baker Street used to be poorly run is now a successful business.

问题补充：

Chan’s restaurant on Baker Street, used to be poorly run, is now a successful business.

A. that

B. which

C. who

D. where

答案：

A. that

(答案→)B. which

C. who

D. where

解析：which used to be poorly run为非限制性定语从句，其中的which指代前面的China’s restaurant。