an还是a eleven boy

请问是an eleven-year-old boy还是an eleven-year old eleven前是a还是an eleven和effect前面冠词用a还是an Bob is (a) eleven-year-old boy.为什么用a不用an? 英语翻译An eleven-year-old boy in a small town wanted to be a tr _____American boy是填a还是an Active boy前面加a还是an 是 a honest boy 还是 an honest boy 是a upset boy 还是 an upset boy an ugly boy 正确,还是a ugly boy 正确 Maomao is an eleven-year old boy.的意思 为什么用an eleven-year-old boy?eleven开头发音不是辅音吗?