should not be allowed to go out at night.
A. Twelve-years-old
B. Twelve-year-olds
C. Twelve year old
D. Twelve years olds
网友回答
A. Twelve-years-old
(答案→)B. Twelve-year-olds
C. Twelve year old
D. Twelve years olds
解析：
这题考查复合词的用法，Twelve-year-olds是指12岁的人，注意在数字+名词的复合词中名词是单数，所以选B。