he is ______boy A.an eight years old B .an eight-year-old

题目

he is ______boy A.an eight years old B .an eight-year-old
两个好像都行啊,奥不懂啊

答案

B.
因为句末有boy这个词,eight-year-old 可做形容词.eight years old 不能做形容词.如果句子没有an 和boy,两者都可以.
不明白的再问哟,请及时采纳,多谢!