It is a good plan in theory but it to be seen whether it works in practice. A. keepsB. s

问题补充：

It is a good plan in theory, but it to be seen whether it works in practice.

A. keeps

B. stays

C. stands

D. remains

答案：

A. keeps

B. stays

C. stands

(答案→)D. remains

解析：考查固定句型：It remains to be seen whether…，是否…还有待证实，句意：在理论上这是好的计划，但是否在实际上能奏效还有待证实。Keep，stay，stand都不可以接to be。选D。