I had been puzzled over the problem for over an hour without any result, ____ all at once the solut...
2023-01-11 07:22:22 69次 四川省2010届高三考前冲刺考试英语试题 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
I had been puzzled over the problem for over an hour
without any result, ____ all at once the solution flashed across my mind.
A. while B.
when C.
then D.
as
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