I think the idea which they have given ________ pretty good in fact.

A.up is

B.in being

C.away to be

D.out are

答案及解析： A

解析：

本题意思是“我认为他们放弃的计划事实上是很不错的．”give up表示“放弃”的意思．is是从句中的系动词．