英语...什么时候是year old 什么时候是years old

英语...什么时候是year old 什么时候是years old 什么时候用fifty-year-old这种形式什么时候用fifty years old这种形式? 他是一个十岁的男孩怎么翻译?years old ,year old 在什么时候不加s? “-year-old” “years old” 1岁时,是 one years old 还是 one year old? 是FIVE YEAR OLD还是FIVE YEARS OLD 请问,“一岁”翻译成英语是"one year old"还是"one years old"? 请问是six-year-old还是six years old还是six-years-old?(这个空签名有个a ) 英语13 -year -old 与13 years old的区别 为什么是she is an eight-year-old girl?she is an eight-years-old 他20岁,是he's twenty year old还是he's twenty years old 请问:是a four years old boy?还是a four year old boy?正确