五、 现在完成时：
1.概念：过去发生或已经完成的动作对现在造成的影响或结果,或从过去已经开始,持续到现在的动作或状态.
2.时间状语：recently,lately,since…for…,in the past few years,etc.
3.基本结构：have/has + done
4.否定形式：have/has + not +d one.
5.一般疑问句：have或has.
6.例句：I've written an article.
It has been raining these days.
I have answered the quesion
The quesipn has been solved
Computer has been invited for many years
Have you been to the USA?
He has gone to home