问题描述：
英语6.Having a trip abroad is certainly good for the old people
6.Having a trip abroad is certainly good for the old people,but it remains _____ whether they will enjoy it.
a.to see b.to be seen c.seeing d.seen
为什么
6.Having a trip abroad is certainly good for the old people,but it remains _____ whether they will enjoy it.
a.to see b.to be seen c.seeing d.seen
为什么
问题解答：
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