请问〔I don't have a mouth〕中间为什么要加〔a〕啊?

请问〔I don't have a mouth〕中间为什么要加〔a〕啊?
请问〔I don't have a mouth〕中间为什么要加〔a〕啊?

请问〔I don't have a mouth〕中间为什么要加〔a〕啊?
a在这里是一张的意思
如果是多张就是mouths了

你（I）有几张嘴呢 当然是一张啊 所以就单数a啊