同学你好，该知识点来自沪江网校《新概念英语第四册【天猫专享】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
次数+in the past+时间，多跟现在完成时连用，比如
The incidence of this disease has dropped considerably in the past few years.
近几年这种病的发病率大大降低了。
The blogsphere has changed a lot in the past few years.
过去几年间博客世界发生了很大变化。
Women have become more assertive in the past decade.
女性在过去十年中已变得更加自信。

祝同学学习进步~