请问是six-year-old还是six years old还是six-years-old?(这个空签名有个a )

请问是six-year-old还是six years old还是six-years-old?(这个空签名有个a ) six-year-old与six-year-olds的区别 six years old 和 six- year- old 和 six- year- olds的区别如题 the six-year-olds是复数还是单数呀 My little brother is ____.A.a six-years old boy B.a six-year-old boy C.a six-years-old boyD.a six-year old boy six years old,six-year-old,six-year-olds在用法上有什么区别?有six-years-old的形式吗? Mary,a ___ girl,is standing under the tree.A.six year old B.six years old C.six-year-oldD.six-years-old everybody, that is ,except his six-year-old daughter这句话that is 怎么理解? six-year-old 为什么不用复数?是合成词?///////////////////////////////////// six-year-old和six years old用法有什么区别? six years old与six-year-old有什麽区别拜托了各位 six-year-old boy和six years old boy 有什么区别?一样么?为什么? his younger brother ,who is ---- ,is in grade oneA six-year-old B six years old C six-year-young D six years young 请问一下到底是sixty-six 还是sixty six,也就是中间有没有减号的? 请问I’m gonna bring my six-year-old daughter to watch you perform tonight.中的to watch you perform tonight ,是什么用法 为什么perform是动词原形? 为什么Six Years Old.中Year要加S呢? Tom is a six-year old school boy. The boy six years old this year.哪里错了 为什么six-year-olds 是正确的