He is a boy, so he can’t go to the park by himself.
A. six-year-old
B. six year old
C. six-years-old
D. six years old
网友回答
(答案→)A. six-year-old
B. six year old
C. six-years-old
D. six years old
解析：
试题分析:此句的基本含义是他才是个六岁的小男孩，因此他不能自己去公园。考查点是六岁的男孩。合成形容词的基本结构。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。故选A