should not be allowed to go out at night.A. Twelve-years-oldB. Twelve-year-oldsC. Twelve

问题补充：

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

答案：

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。