He is a boy so he can’t go to the park by himself.A. six-year-oldB. six year oldC. six-y

问题补充：

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

答案：

(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