since 是不是经常和 has down 连用?

since 是不是经常和 has down 连用? Since (retiring) from the company,she has done.为什么要用ing?和since有关吗? has since been 什么是Dow Jones?手机报经常提到这个但是,我都不知道是什么,代表的是什么它的上升和下降代表什么和我们的生活有什么联系,能给我们的生活带来什么? ever since 和since 的用法和意思有什么区别是不是一样的? 英语翻译是不是翻译为：it is 3 years since he has smoked. have/has+短暂性动词+since对吗?是不是短暂性动词也可以换成延续性动词. we don't know what has happened since yesterday since 不是跟延续性动词吗为什么用has happened是不是happen也可做延续性的， dow是什么意思 DOW是什么意思 mini dow ever since 和since 有什么区别Mr li went to America 20 years ago and has bee there ever since.后面为什么是ever since?不是ever since要和现在完成时连用吗?这里怎么会是过去时态啊? it has been since.用法 Has和have的区别是不是Has是单数啊 It is 3 years since he joined the army 和It has been 3 hours since he left his office.为什么一个用is一个用has been until 和 since的区别until 和 since 都有直到的意思,两个有什么区别 是不是until后要跟句子 since 后要接单词 初二英语现在完成时延续性动词是不是出现for +段时间 或since+时间的时候才特别要用啊?比如 my sister has bought a book in the shop already 和 my siter has had a book in the shop .是不是区别在这里呢?那么 my s she has lived in guiyang since 2000 该疑问句和否定句.