I have stayed in beijing for a months

问题描述:

I have stayed in beijing for a months

应该是I have stayed in beijing for a month
我在北京待了一个月

应该是a month,表示单数啦
我在北京已经呆了一个月了

我已经在北京呆了一个月了 months 前面有A 后面就没S 如果没A 有S 就是带了几个月了