题目内容：

This is a_boy.He can't look after himself A,four-years-old.B.four-years-olds,C,four- year-old为什么

优质解答

选C
解析：four-year-old 和four years old都可以指“四岁”,但用法上有不同.
前者只能用在名词和人名前,作定语.后者只能用在名词、系动词之后,作表语.
翻译：这是一个四岁的男孩子,他不能照顾自己