sisteen-year-olds的后面为什么要加s

sisteen-year-olds的后面为什么要加s shouldn`t sisteen-year-olds be allowed to work at night? 16岁的人不允许在晚上工作?如果回答是的,不允许该怎么回答,如果回答不是的,允许该怎么回答 为什么six-year-olds 是正确的 five-six-year olds是什么意思与five six-year olds的区别是什么 six-year-old与six-year-olds的区别 15-year-old与15-year-olds的区别 year-olds与year-old的区别16-year-olds与16-year-old有什么区别吗? fifteen-year-olds是什么意思? seven-year-olds Twelve-Year-Olds翻译 16-year-olds 与the+形容词的区别 16-years-old和16-year-olds的区别 Craig创办的 the twelve twelve-year-olds怎么翻译 Sisteen-year-olds___(be)not allowen to drive. three-year-olds汉语意思 year olds还是years old? sixteen-year-olds可以直接使用,sixteen-year-old不可以直接使用后面要加boy? 16岁的男孩们 英语怎么说sixteen-year-olds boy和sixteen-year-old boys哪个对?还有sixteen-year-olds对么？