what is this ?It is a pen而不是It is pen.但为什么what's this? It's N.就是正确的?N前不能有冠词吗?

问题描述:

what is this ?It is a pen而不是It is pen.但为什么what's this? It's N.就是正确的?N前不能有冠词吗?

N = a pen 可以这么理解