she doesn't have sisters.Her mother doesn't have sisters,too怎么改?前半句 为什么没有姐妹 说的是 doesn't have sisters sister后为什么有s？

she doesn't have sisters.Her mother doesn't have sisters,too
怎么改?
前半句 为什么没有姐妹 说的是 doesn't have sisters sister后为什么有s？

too 改成 either
否定句里的 ”也是“ 用 either
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have no 加名词,用单数
don't/ doesn't have (any) 加名词 用复数
也就是说 I have no sister = I don't have (any) sisters.

她没姐妹，她妈妈也没姐妹
she doesn't have sisters，neither does her mother.

把too改成either，否定句的“也”用either
因为sister是可数名词，用可数名词的时候，可以1）单数形式，但是前面必须有定语或指示代词the that或冠词a an.或any2)复数形式
这里sister前面没有这些，所以用复数形式。不明白的话继续问