Is Qinghai-Tibet Railway plays an important role in China’s railway history the topic that you’re ing to?
A. it
B. that
C. what
D. this
网友回答
A. it
(答案→)B. that
C. what
D. this
解析：句意为：青海至西藏的铁路在中国历史上扮演着重要的角色就是你要谈到的话题吗？本句的正常语序为: Qonghai-Tibet Railway plays an important role in China’s railway history is the topic that you are ing to. 所以此处应是主语从句，从句中不缺少成份。故答案应为B。