These diagrams are especially helpful when we have a concrete problem ________ at hand. A．be solvedB...
2022-11-26 08:09:21 181次 2014年高考二轮复习热点预测：专题6非谓语动词英语试卷（解析版） 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
These diagrams are especially helpful when we have a concrete problem ________ at hand.
A．be solvedB．to solve
C．solvedD．being solved
本题链接：
