Several of my friends 可以改成my Several friends 为什么一定要加那个of

Several of my friends 可以改成my Several friends 为什么一定要加那个of a friend of my还是a friend of mine several thousand 和 several thousands of 的区别及具体用法还有这一题：There are_____students in my school A.several thousand B.several thousands of I bought ________（几个）present for my friend. 出了several,可否填some? take good care of yourself.my friend, a friend of mine=?my friends Most of my friend are student 改错 For ten of my most important friend thanks of my friend是什么意思?是什么意思啊? Mike is________.A a friend of me B one of my friend C one of my friend D the friend of my 英语翻译a friend of my father's还是a friend of my father,如何辨别, I think you of my friend还是I think of you my friend? 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?