They have been working very well this term. 这学期他们学习很好。
They have worked very well this term.
It has been raining for two hours. 下了两个小时的雨。
It has rained for two hours.
I have been hearing from her regularly. 我定期收到她的来信。
I have heard from her regularly.
We have looked for mushrooms but have not found any. 我们找寻蘑菇但一无所获。