for后加一段时间 ,但不能错误地认为for加一段时间就是完成时.同样 since 后加具体过去时间或过去时的句子,如果跟一般现在时时,since 表示“既然、由于”之意. 例 for three days I have been here for three days. I stayed there for three days. Now, I well remember that time. I will stay there for three days there, then I will go to Australia. Since three days ago, I have been here.
