1)Shehas realized that she is wrong at this matter, so she feels very sorry.
2)Shehas realized that she has been wrong at this matter, so she has felt verysorry.
3)Sherealizes that she is wrong at this matter, so she feels very sorry.
4)Sherealizes that she has been wrong at this matter, so she has felt very sorry.
5)Shanghaiused to be a small town several hundred years ago, now it has become a largecity.
6)Shanghaiused to be a small town several hundred years ago, now it is/becomes a largecity.
请教老师，以上1)和2句，3)和4)句，5)和6)含义的理解到底有无差别？假如有，麻烦老师比较一下，谢谢！
麻烦老师就上面3组句子比较剖析含义差别，用一般目前时和完成时的语境理解差别？谢谢！
我觉得，用1)She has realized that she is wrong at this matter, so she feels very sorry. 其它不适合。由于完成时在这里强调对目前的影响或者与目前的联系，感觉抱歉是由于已经认识到，最直接的训练不是错了。所以认识到用完成时，而且感觉到用完成时表达训练没意义，合理感觉遗憾就是前面认识到致使的结果。结果用一般时态表达最好，仅需称述一个事实即可。
5)Shanghai used to be a small town several hundred years ago, now it has become a large city.我觉得这个比6更能表现变化之大，用完成时表达出改变致使目前与过去对比差异之大。
