did a boy friend of my sister's go to the party?这句有错吗

did a boy friend of my sister's go to the party?这句有错吗 My sister's boy friend是什么意思 she is a lovely teacher.The names are my friend's 这两句话有错吗? The girl talking to Mary is a friend of (Mary's sister's).括号 the,in,girl,my,red,a,friend,is,of,sister's(.) a friend of my sister's是什么意思? one of my sister's friend 后用加S吗 The girl talking to Mary is a friend of＿. A.Mary's sister B. A man beside me is my sister's friend.这句英文错在哪里 this is a card （ ） my friend to me let's go to visit the hom 这句有错吗：The man a friend of whose is ill is worried that he wi It is old enough for the boy to go to school.这句英语的语法哪有错?