问题补充:
It is a good plan in theory, but it remains whether it works in practice.
A. seeing
B. to see
C. seen
D. to be seen
答案:
A. seeing
B. to see
C. seen
(答案→)D. to be seen
解析:考查remain的用法:句意:这在理论上是个好计划,但是在实践中是否奏效还有待证实。Remain后面接不定式,表示“仍然要做…”,因为it和see是被动关系,用不定式的被动式,选D。