there has been a time和there had been a time有什么区别?

There has been a misunderstanding. Tim is in Australia.How long _____ there?(a)is he (b)has he been (c)has he (d)was he这个是选b吧,想问下,选a行么?ab两个意思有什么区别? ( )Tim _____ the school basketball team for three weeks.( )Tim _____ the school basketball team.( )tim _____the school basketball team activities.a.has jioned b.has jioned in c.has been d.has beenon 新概念2第四课里面都用了什么时态have just received a letter from my brother,Tim.He is in Australia.He has been there for six months.Tim is an engineer.He is working for a big firm and he has already visited a great number of different p 关于新概念二册第四课的问题I have just received a letter from my brother,Tim.He is in Australia.He has been there for six months.Tim is an engineer.He is working for a big firm and he has already visited a great number of different places 小学阅读英语习题7道.An exciting trip激动人心的旅行 I have just received a letter from my brother,Tim.He is in Australia.He has been there for six months.Tim is an engineer.He is working for a big firm and he has already visited a grea 新概念2 英语lesson4 An exciting trip 课文和问题如下I have just received a letter from my brother,Tim.He is in Australia.He has been there for six months.Tim is an engineer.He is working for a big firm and he has already visited a great nu there has been a time和there had been a time有什么区别? Tim ___since he lost his job three weeks ago.A) had been unemployedB) was unemployedC) has been unemployed D) has unemployed Yellow of the evening,Tim has been very,very beautiful. It has been there since a t_ years ago . there has never been a better time to esgapt there has been的用法 there has been a need for sth 不懂为什么是there has been?真是什么时态呢,. Tim has been abroad for three years.（TIM出国已经有三年） 我想问,为什么不是 tim has been to ,加TO ,为什么错 there has been...为什么要加been? He knows a lot about Egypt.I heard he( )there before. A.has been B.has gone C.had been. ---Where is your uncle?---He to Hong Kong.He there for many times.A.has gone;has beenB.has been;has been C.has gone;has gone D.has been;has gone