为什么要说the/a two-year-old boy 不能说two years old boy

为什么要说the/a two-year-old boy 不能说two years old boy the boy is _ older than his brother.A.two years B.two-year为什么选A? two editions a year the year 2011 should be read the year ( ) a.twenty eleven a.two thousand and eleven b.twenty eleven选B.为什么? the year 2011 should be read the year ( ) a.twenty eleven a.two thousand and eleven b.twenty eleven选B,为什么? The two-year-old boy is the only person____of his family in the earthquake.A.alive B.living C.live D.lively选哪个?为什么? a year or two 还是one year or two 【单项选择,要说为什么选这个答案】 It took the workers half a year（）the high building.【单项选择,要说为什么选这个答案】It took the workers half a year（）the high building.A.builds B.to build C.building D.buildMr. the other two being the Autumn Moon Festival and Chinese New Year.为什么用being? we know this area,two hundred years ago,was a lake__two-thirds of the size at presenttwo-thirds its present size要说为什么 Aftr the end-of-year exams,we shall have ( )vacation.A.two month B.two-month C.a two -month D.a two months hey built a bridge between the two islands last year.改成疑问句They built a bridge between the two islands last year.改成疑问句 the ___month of the year is february.A:one B:first C:two D:second The boy is _______ than his brother.A.two yearThe boy is _______ than his brother.A.two years older.B.two years elder.C.two-year older.D.two-year elder. A highway being constructed between the two cities will be finished next year.这道题中“being constructed ”的用法是怎样啊?为什么这样用?做什么句子成分 More than two __visitors come to the island for their holiday every year.A.millions of b.millions C.million of D.million为什么选D [ ][ ](two) momth of the year is [ ] the town has set up another hospital___ a.this year b.last year c.in May d.for two years答案是a,不过为什么啊?求解释,在线等速度谢谢