for
for the past forty years后跟什么时态？
the past forty years后跟什么时态？
现在完成时
They have enjoyed good harvests for the past several years.
过去好几年他们都获得了好收成.
He has not been near the office for the past three days.
过去三天他一直没有去办公室上班.
for the past 40 years句子用什么时态？
正确的应该是in /over the past 40 years句子用现在完成时态，现在完成时指的是过去发生的动作对现在造成的影响。其结构为have/has done 。中文意思是“在过去的四十年”
例如，在过去的四十年，在党的英明领导下，我的家乡发生了翻天覆地的变化，全体时民已过上小康生活。
In the past forty years, under the wise leadership of the Party, earth-shaking changes have taken place in my hometown, and all the people have lived a well-off life.
in the past three years什么时态？
in the past three years：在（刚刚）过去的三年里 用现代完成时
in the past three years与
现在完成时连用.
in the past是过去时,in the past 一段时间是完成时.
如：Tom went home in the past.
We have seen him 3 times in the past 3 years.
现在完成时
1.表示一个动作开始于过去,持续到现在(也许还将持续下去)。表示从过去持续到现在并包括现在在内的时间状语有:lately, recenly, in the last/past few days/years, since then,up to now,so far等。
如:
In the past three years, the cooperation between our two countries has been successful.
在过去的三年里，我们两国的合作很成功。
He has been busy writing a book recently.
最近他一直忙着写书。