that's OK/all right/right ,Not at all,it doesn't matter ,nev

that's ok 与that's all right,that's right ,it doesn't matter,never mind都有 没关系 之意,可用于回答表示 抱歉或不客气 语义的句子.如：I'm sorry.That's all right.或 Never mind.
Not at all 意为 一点也不 ,用于回答有目的性的问句.如：Are you hungry?No,not at all.(你饿吗?不,一点也不饿.)