都是正确的.two-hour作为一个类似于形容词的存在,有了“-”就不要加s了.two hours‘ 是直接修饰的,因为hours是复数,所以“一撇”要加在s后面附上两个例句：The town is two hours' drive from here.It's a two-hour-...two-hour-drive一定要在hour和drive之间加—吗two-hour drive也对吗hour和drive之间是不需要“-”的，因为two-hour是作为定语修饰drive的，drive是一个独立的名词~后面一个是对的，前者“two-hour-drive”是错误的。那例句中It's a two-hour-drive distance from here.是怎么回事有一道选择题two-hourtwo hours'两个选项都有，选哪个你要看前面有没有冠词a，如果是two-hour的话，前面必须有冠词，因为这是定语修饰名词，名词需要冠词。而two hours‘不需要冠词，你可以再看一下前面的例句，这两个虽然意思一样，但是用法是不相同的。例句：The town is two hours' drive from here.It's a two-hour-drive distance from here.如果two-hour-drive全部连起来就是表示’两个小时车程“的意思。我前面理解错误了，two-hour-drive是正确的哦~意思就是说two-hour-drivetwo-hour drive都对，但two-hour-drive 为形容词可在形容其他，而two-hour drive就已经是名词了是吧是不是只有one— year—old boy 没有one years old' boy是的，这里one-year-old整个作为一个形容词的成分，如果要分开来说，只能说是：This boy is one year old.