She helps her mom and she is tired.
她帮助了她的妈妈,然后她累了.
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不能够用 She is tired and her mom helps she .
因为 helps 后跟宾语,不能跟主格的 she.
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虽然语法上 She is tired and she helps her mom.是对的
但是是她帮她妈妈在前,然后累了,比较符合逻辑.
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所以用 She helps her mom and she is tired.