1.the apple was eaten by one of my father's friends

1.the apple was eaten by one of my father's friends
2.the apple was eaten by a friend of my father's
3.the apple was eaten by a friend of my father
4.the apple was eaten by my father's friend
要求翻译 苹果被我爸爸的一个朋友吃掉了
第一句和第二句据说是正确的~
我写的是第三句为什麽不可以呢?
如果要求是 苹果被我爸爸的朋友吃掉了 是不是就可以了呢?
第四句friend后面用加s麽?如果是想用friend怎麽改呢?
问了这麽多..