为什么 in the last few years 用完成时态一般都直接说它是标志词

过去完成时，过去式，也有可能是现在完成时啊。要看句意。

现在完成时可以表示“已经完成”的动作，也可以表示“未完成”的动作。与其连用的时间状语
往往是指一段时间的状语以具体表示某一动作或状态持续了多久。如：
1. since + 具体时间，表示动作或状态从何时开始
Since then, he has developed another bad habit.
自那以后他养成了另一个坏习惯。
He hasn't been home since he graduated.
他毕业后就没回过家。
2. for + 一段时间，表示动作或状态持续了多久
We have worked here for ages.
我们在这里工作很久了。
There has been no rain here for nearly two months.
这里已经近两个月没有下雨了。
3. until now, up till now, so far, up to the moment
到目前为止
I have not seen him so far.
到目前为止我没见过他。
Up to the present, everything has been OK.
到目前为止一切正常。
4. in/during the past/last five years
在刚刚过去的5年里
He has been away from school during the last few weeks.
过去的几个星期里他没在学校。
In the past few years they have dealt with quite a few international corporations successfully. 在过去的几年中他们已经和好几家跨国公司做成了生意。
5. all the while, all day 一直，一整天
She has been busy all day.
她忙了一整天。

非常简单：1 in the last few years ==since the last few years ago .又如：He has lived there in the last five years==He has lived there for 5 years.==He has lived there since 5 years ago.2 in the past--...

意思为：在过去的几年中
last的意思过去