一道选择题,要求解释Yesterday I bought four _____ books for just 10 do
一道选择题,要求解释 Yesterday I bought four _____ books for just 10 dollars. A.three-dollar B.three dollars 想知道为什么用B不可以. 一个五岁的男孩不是可以用a five-year-old boy或a five years old boy吗? 那为什么一个五岁的男孩可以用a five-year-old boy或a five years old boy呢?