表示从过去某时开始一直延续到说话时还在进行,或可能还要继续下去的动作.它通常和“for+段时间”或“since+点时间(也可以是从句)”的时间状语连用.例如：
I have been waiting for a letter from my parents.我一直在等我父母的来信.
It has been raining for three hours.
雨已经下了三个小时了.
We have been studying here since 2004.
自从2004年以来,我们一直在这里学习.
2.表示从过去某时开始,一直延续到说话时刻,可能刚刚结束的动作.例如：
She has been sweeping the street all day.She is too tired.
她一整天都在扫大街.她太累了.
We have been waiting for you for two hours.We don't want to wait any longer.
我们已经等你两个小时了.不想再等了.