They are smiling. There ______ much trouble solving the problem. A. couldn’t beB. mustn’t be C. can’...
2022-10-15 15:10:02 99次 2016届天津河东区高三第二次模拟考试英语试卷（解析版） 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
They are smiling. There ______ much trouble solving the problem.
A. couldn’t beB. mustn’t be
C. can’t have beenD. mustn’t have been
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