（问下,1题的brought是不是打错了?原文应该是bought吧?）
1.I have had the piano for six years.
原因：bought是瞬间动词,不可以与时间段连用,应换成had.
2.-where have you been?
-I've been to school.
原因:been和gone的区别在于,gone是指某人去什么地方还没回来,不在此地；而been则是某人去什么地方已经回来了,在这里.
（是不是打错了,少了主语?）
3.How many pages had you read by the end of last year?
原因：当出现by+时间段,要用had.过去完成时.
（whine是while吧?）
4.While I walked in the street,I met my teach.
原因：遇见某人要用meet（met为过去时）,see（saw为过去时）是指看见了什么,不能解释遇见.如：While I walked in the street,I saw a dog sitting in the corner.
5.They had their lunch at twelve.
或者：They have had their lunch.
原因：现在完成时不能与明确表示过去时间的状语连用.
6.The workers have repaired the machines just now.(同上,去掉have或者just now)
7.You have waited here since two hours ago.
或者You have waited here for two hours.
原因：现在完成时里表示时间段,since…ago,或者for+时间段.
8.She siad she had forgotten to do her homework.
原因：forget-forgot-forgotten.现在完成时中has/have+过去分词
9.His grangpa is over seventy,but he is still in good health.
原因：be in good/poor/… health 健康状况好/不好.固定的短语搭配
（终于打完咯~希望能满意.自认为英语还不错,有什么关于英语的问题可以在QQ上问我304145153~）