现在完成时（非延续性动词）与过去完成时都发生在过去，要如何区别

现在完成时（非延续性动词）往往出现在一些特殊的语言环境中，这时的完成是类似于汉语中的“刚才”

在某些疑问句中表示很近的过去：
Where have you been?
What have you done?

这种过去往往是没有时间状语的，如果句中出现just now这样的时间状语，那就还用过去时，即使要表达的意思完全相同

一般过去时一般都需要时间状语

现在完成时用非持续性动词还可以是句子为否定句的情况

I haven't finished my homework yet.

下面是这两种时态的用法总结：

现在完成时：

用法：

（1）表示已经完成的动作

（2）延续至今的动作，常与for、since等连用：
We have been good friends since our middle school days.
We have studied English for six years.

（3）用在条件或时间状语从句中，表示将来某个时间之前已经完成的动作：
He will come as soon as he has finished the homework.
If you have read the book before I leave, please lend it to me.
We shall wait here until the rain has stopped.
Won’t get off the bus until it has stopped.

（4）某些疑问句中表示很近的过去：
Where have you been?
What have you done?

（5）先行词用序数词修饰的定语从句：
It is the first time that I have been to the Great Wall.

注意：