it is 3 weeks since he worked here 啥意思,请专业些的人解答

改错：It is 3 weeks since Ihave seen him. it is 3 weeks since he worked here 啥意思,请专业些的人解答 Is it two weeks since he left London 可以这样改吗He has been to London for two weeks It is two weeks since we met last time 是什么从句? 1 He came to our village two years ago.=He our village since two years ago.2 He left home three days ago=He home for 3 days.3 I bought the watch 2 weeks ago=I the watch since 2 weeks ago.4 It is 5 days since I borrowed the book=I the book for 5 days. 改错句:It is two weeks since I have seen him要说出具体原因,确切点 It's three weeks since you were ill(什么意思) it is 3 years since Tom has been abroad it's been several weeks since he___(join) the music club有since的话后面要用什么时态 It has been two weeks since I last wrote to you.意思? 初二英语单句改错,急...1、You must do it like（A） the teacher told（B） you,or（C）you may make a few（D） mistakes.2、It is（A） two weeks since（B） I have seen（C) him(D).3、I am(A) very pleased(B) I have seen(C) as good(D 英语现在完成时的延续性动词he borrowed the book 2 weeks ago 该写it was 2 weeks since he bought the book还是it has been 2 weeks since he bought the book 英语翻译It is 3 years since they got marriedIt is 3 years since they married求翻译.为什么都是since可意思完全不一样诶 It is five years since he smoked It is two weeks since I have seen him.( have seen-- saw)谁能够帮我讲出一个所以然?麻烦题目看清啊——就是把HAVE SEEN改成了SAW 这是为什么？什么理由？ It is 3 years since he joined the army.为什么用is不用has been it is 3 years since he has been a doctor 怎么翻?还有it is 3 years since he was a doctor 怎么翻译1? 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had been