mum,this is mr green,my english teacher.为什么是this 不用he?

mum,this is mr green,my english teacher.为什么是this 不用he? Mr Green is my English teacher.He t______us English well. whose Mr Green?he is my english teacher改错题 My English teacher is Mr Green.对Mr Green提问 Mum,this is my teacher,Miss Li This is Mr Green Hi,____Nancy.____am a girl.___is my teacher,Mr Green.This is This is my teacher , Mr . Wu是什么意思? Mr.green is my english teacher ___________very much 选择填空：Mr Black,__my English teacher a.she is b.he is c.this i Mum,this is my teacher ,Miss Gao.-----------________? teacher this my woman is English