_______that time,the reform had begun to take effect,and the economy had begun to take off .

分类: 作业答案 • 2021-12-28 14:34:14

问题描述：

_______that time,the reform had begun to take effect,and the economy had begun to take off .
中为什么要选择by 而不选择at

答

by.有“截止”之意,表示一段时间；而at.是个时间点,与后面的完成时态不相符合.