是an one还是a one

是an one还是a one 是a one-hour ducumentary还是an one-hour documentary a one -hour还是an one-hour 英语翻译是one and a half hours还是one and half an hours还是其他? one前是用a还是an,如：such a one 还是 such an one. one 前的冠词是a 还是an? 冠词 an one-hour 还是a one-hour 是a one-year-old boy还是an one-year-old boy 关于an apple a day,keeps the doctor away到底是an apple a day an apple one dayone apple a day还是one apple one day useful one前用an还是a 形容词+one前面用the 还是 a/an比如说 beautiful one useful one is russia a(an)European country or an Asian one ;an 还是an;an one-year-old boy 前面是填a还是an呢? one－year-old前面用an还是a one前加a还是an?RTRT 谢谢!不是这个one 诗one-day 这个形容词前加什么 是less than an hour还是less than one hour? a,an,one的区别 是the other one 还是 another one 还是 other one