a two-minute-walk,这种表达方式为什么不对,如果要更改这个的话,应该怎么改,但是答案显示a two-mi

Between two classes we have a ___break.A ten-minute B ten-mi a two-hour walk 和 two hour's walk中为什么前者加a后者不需加a? a-a等于2a对吗,不对的话怎么改/ 英语中一两分钟怎么表达?是one or two minutes 还是one minute or two 还是 a min A 20-minute walk为什么与20 minutes' walk 相同? "a coloured cloth is cover whit the sofa."这句话对吗?如果不对应该怎么改? we often have a ten-minute b_ between two classes two and a half hours' walk可不可以说two hours and a half's walk 这个主语从句对吗?what the room i like is with two windows,如果不对求改一下, a twenty-minute-walk or a twenty-minute's walk 简单英语问题It's two hours' walk.=It's a two-hour walk.为什么前面的不要加a, 急 英语during the three decade这句话对吗?如果不对 该怎么改?改成two吗?