I have been an engineer for more than ten years,but I was once a worker for three years.这里was once a worker 为什么不是had been a worker?

`I have been an idiot!' I have never been to ____ AmericaA.an B.the I have been there for half an hour.啥意思 Ive never been to an aquarium.下一句是 Neither have I还是So have I an not sure how long they____A.have married B.have been marriedC.have been married D.married I have never been to an airport before.可以改成：I have never gone to an airport before.RT I have been selling I have been trying I have ever been I too have been I have been to. I have been I have been in. Have you been to the cinema?- yes,I have.I_____there an hour ago. I have been to Tai'an.He has been there,too.组成一句___ ___ I ___ ___ he has been to Tai'an 请帮我区分一下这三个句子I have been writing an article.I have written an article.I wrote an article.重点区分后两个 what an idiot i'd been!been! I have been to shenzhen _______ A.so an I B.so i am C.so have i D.so i have B.