I am a chinese boy.这个 chinese boy前面要加a吗?

I am not Chinese boy I am not a Chinese 为什么后者要加a那 I am a chinese boy.这个 chinese boy前面要加a吗? I am a chinese boy .(变复数） I am a boy. I am Chinese boy.chinese为什么不能用china代替 i am proud i am a chinese I am a Chinese还是I am Chinese 是i am a chinese 还是 i am chinese I am Chinese.I am a Chinese.哪个句子正确 I am 12 years old boy of chinese.什么意思 i am a man.not a boy I am.boy,but she is .A.Chinese,EnglishB.Chinese,a EnglishC.a Chinese,an EnglishD.an Chinese,a English(排除B.D后,应该选那个,要原因)English好像是不可数的吧，能加an吗？ I am a Chinese和I am Chinese哪个对?我老师说“I am a Chinese 是错误的句子,除非在后面加boy或girl才对”,但我看的课外书上却有I am a Chinese. I am a China girl还是Chinese 把这篇短文改成第三人称.我来不及分大小写了都写小写了hi,myname is daming.i am a chinese boy.i am thirteen years old.i am a student in no.3middle school.i am in clsss thre,grade seven.my favourite sport is basketball.i like swim I am a blue boy的意思 i am a boy. 错在哪里? I am a [ boy,girl]中文是什么