A booking-office is a place tickets are sold.A. whenB. whereC. whyD. which

问题补充：

A booking-office is a place tickets are sold.

A. when

B. where

C. why

D. which

答案：

A. when

B. where

C. why

(答案→)D. which

解析：在非限制性定语从句中只能用which，故选D。