为什么用It is my aunt,不用She is my aunt

为什么用It is my aunt,不用She is my aunt （ what ）is she -------she is my aunt 为什么用what 而不用 who 还有she is my aunt中的my aunt提问, she is my aunt (对my aunt 提问） my aunt is a teacher.she ____english 改错题：She is my aunt Mary. She is my aunt Mary.(找错） she is my aunt改为同义句 She is my aunt对myaunt提问 she is my aunt 改为复数形式 she is my aunt (提问） she is my aunt .同一句