should not to be allowed to work at night.A. Sixteen-year-oldsB. Sixteen-years-old C. Six

问题补充：

should not to be allowed to work at night.

A. Sixteen-year-olds

B. Sixteen-years-old

C. Sixteen year olds

D. Sixteen-years-olds

答案：

(答案→)A. Sixteen-year-olds

B. Sixteen-years-old

C. Sixteen year olds

D. Sixteen-years-olds

解析：句意：16岁的孩子们不应允许夜间工作。形容语转换成名词，表示某一类人，故选A。