Millie is one of my best and she is a girl.
A. friends, friend
B. friend, friendly
C. friends, friendly
D. friendly, friend
网友回答
A. friends, friend
B. friend, friendly
(答案→)C. friends, friendly
D. friendly, friend
解析：句意：米莉是我最好的朋友之一，她是一个很友好的女孩。one of +形容词最高级+名词的复数形式，表示“最…之一”，friendly友好的，故选C