a.John didn't accept it,because of Mary.b.John didn't accept it because of Mary.有什么区别

问题描述:

a.John didn't accept it,because of Mary.b.John didn't accept it because of Mary.有什么区别

一个不限定,
后一个限定

a加了逗号表示逗号后面是个原因状语从句,而b则只是一个短语而已、、、

没有区别,只是a句停顿了一下,类似于补充内容.
b句说的很连贯,because of Mary 好像就是说话者 要着重表达的
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