a 15-year-old b 15-years-old c15-year-olds d15 y

a 15-year-old b 15-years-old c15-year-olds d15 y year olds还是years old? fifteen-year-olds和a fifteen-year-old boy “-year-old” “years old” 16-years-old和16-year-olds的区别 sixteen year olds 还是sixteen year old? six years old 和 six- year- old 和 six- year- olds的区别 16-year-old和16-year-olds和16 years old有什么区别? She is a____girl.A.9 years old B.9-years-old C.9-year old D. 15-year-old 与15 years old 的区别 two( )twins. A. nine-years-old B. nine-year-old C. nine year My young brother ___be 15years old next year A is going to B