Many provinces have been hit with smog. If _______ unsolved, the problem may lead to more serious re...
2022-11-28 15:56:09 12次 2013-2014学年福建省莆田一中漳州一中高三上学期期末联考英语试卷（解析版） 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
Many provinces have been hit with smog. If _______ unsolved, the problem may lead to more serious results.
A. having left B. to leave C. left D. leaving
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