since与ago这两个词都怎么用啊?

since与ago这两个词都怎么用啊? 在现在完成时态 since 引导的句子中,主句的谓语动词必须用持续动词吗?He has left here since two years ago.He has been away since two years ago.是两个都对,还是有错? 在英语中before与since与for与ago在时态的不同?用在什么时态?在英语中before,since,for,ago在用在什么时态?怎么用?回答时请举简单例子,不要太长篇大论, since two years ago与since two years的区别,分别用在什么时态? 对since two weeks ago提问用什么词 since,so far这两个词都必须用在现在完成时吗 since能与ago连用吗 since能否与ago是连用哦 My husband became a teacher 15 years ago.(用since或for改写） 怎么写啊. since引导时间状语从句since引导的从句怎么用这句话有错吗?since 21 century ago,the computer is wide use for personal daily life.怎么改 一般过去时VS现在完成时 时间标志He has dead since a year ago.He dead a year ago.这两个句子用了不同的时间标志就成了不同的两种时态.我想问下一般过去时与现在完成时的时间标志有什么不同?(以这 since three years ago 句子要用在 现在完成里吗?We __B__ english since three years ago.A.learned B.have learned Tom has been in Paris since 2 years agoI have been here since five months ago.问：1.since+时间+ago 在句子里怎么翻译, John joined the army three years ago.(用since或for改写） 怎么写. since,for,ago与时间搭配的意义曲别 since ten years ago怎么变特殊疑问句 since能不能与ago 连用,与for有什么区别.since具体有什么用法? since long ago 这两个英语句子有何区别1.I have studied English since three years ago.2.I have been studing English since three years ago.他们在表达上有何区别,或者有没有什麽错误?