“A friend of my sister”表达正确吗?还是应该是“A friend of my sister's”?

This is my friend 和 These are my sist 改成否定句怎么改啊,急... a friend of my还是a friend of mine a friend of mine=?my friends 英语翻译a friend of my father's还是a friend of my father,如何辨别, a friend of my father和a friend of my father`s的区别? a friend of my father? a friend of my father's?两种说法哪个对? a friend of my brother和a friend of my brother's 有什么区别? a friend of my brother 还有a friend of my brother 两者什么区别? “A friend of my sister”表达正确吗?还是应该是“A friend of my sister's”? 是a friend of my mother对,还是a friend of my mother's对? Mike is________.A a friend of me B one of my friend C one of my friend D the friend of my a friend of Tom表达对,还是a friend of Tom's对a friend of my father对，还是a friend of my father's对 A friend of my请问这里使用my对吗? Mr Smith is____A a friend of my fatherB a friend of my father'sC my brother friend D my brother friend's解析并翻译! A friend of her/his,那就是说a friend of my?那和a friend of mine有什么区别? One of my friends等于a friend of mine吗? She is a friend of my正确还是She is a friend of mine正确? a friend of mine = a friend of my friends 吗?