为什么do,does后面不加s

the children go to school by bus.为什么后面加do 不加does Nobody can live without water?中live加s还是不加s为什么?还有 （Do,Does）an she is English后面为什么不加does? to do some exercise 为什么exercise 后面不加S啊 不可数名词后面加do还是does? many people 后面加do还是does Do you like kites?kite后面为什么加s? Do you like bananas?后面为什么要加s Do you have some pape?这句话中已经说有一些了,为什么paper后面不加s Does tom do morning exercises every day?exercise后面为何加s? 句子中有do\does,后面第三人称的动词还要不要加s? lots of practice后面的practice为什么不加s?