has been doing sth+介词后接时间的介词是in/for/since?

Have/has been 后一定要加doing sth.吗? have(has) been doing sth 造句写翻译 have been doing sth has been doing sth+介词后接时间的介词是in/for/since? has difficulty doing sth还是has difficulty to do sth have been doing sth是什么时态? has been doing have been done区别 sth has changed 还是 sth has been changed i has been doing 还是i have been doing HAV BEEN DOING STH为什么要加BEEN? have been doing sth had 加过去分词 have has 加过去分词 分别是什么时态?求什么区别?最好有例句、、 Her grandfather died seven months ago.(改为同义句)Here grandfather _____ _____ _____ for seven month.= has been doing sth？ 现在完成进行时的谓语动词构成 I/ we/ you/ they have been doing sth.he/ she/ it has been doing sth.（一）表示从过去某时开始一直持续到现在的动作,并且还将持续下去.The Chinese have been making paper for two thou had been doing是什么语法?举个例子~有have/has been doing的说法吗? have /has been doing 是什么句型啊做题时遇到的 翻译句子：he has been doing nothing else ever since. That we are doing has never been done before.改错 They have been doing their homework能改成：he has been doing their homework 吗?have改成了has