It remains whether Liu Xiang will take part in the next Olympics.A. to see B. to be seenC

问题补充：

It remains whether Liu Xiang will take part in the next Olympics.

A. to see

B. to be seen

C. seeing

D. to have seen

答案：

A. to see

(答案→)B. to be seen

C. seeing

D. to have seen

解析：考查固定句型。句意“刘翔是否会参加下一届奥运会还有待观察。”It remains to be seen...“......还有待观察”。故选B。