Question

Although he is only a _____ boy. He knows a lot.

A．five year old

B．five-year-old

C．five-years-old

D．five-year-olds

Answer 1

B

试题分析:根据语境和选择项的提示可知此句的含义是虽然他只有五岁，但是他知道的很多。此题考查的是合成形容词的基本构成。根据语法知识可知选择C。
点评：合成形容词的基本构成，数词+名词(+形容词)；合成形容词中的名词(year, hour, metre, month等)必须用单数形式。