I AM FROM ___USA 这里要加the吗?还要说明为什么

I AM FROM ___USA 这里要加the吗?还要说明为什么 I come from china.可以说I am from china.为什么这里不加be动词am了? i am being的问题i am being serious i am being from china i am being an engineer这里的being 请提供准确答案 参考书籍 i am from I am from the USA为什么要加am Am I from Canada?呵呵, I am from outer space. I am Aaron from England. i am d____ from you I am finished 这里为什么要用be finished? My sister is taller than I am.这里为何要用I am?可不可以把am去掉? I am usually hungry when I get home from work.请问这里的from work是惯用的嘛?能否具体点，比如说有例句呢？ 我从我所做的事中得到了教训.I（ ）from what I have done.括号里该怎么填?I am looking forward to seeing you again.请问这里为什么要用looking呢? i am a girl.i am from xining. i am a girl from I am a girl feom I am from Beijing.I am a G_______girl. I am/come from 还是I was/came from? From now I am just for