选择题：7. (单选题)一次文献、二次文献、三次文献是按照( )进行区分的。

题目内容：

7. (单选题)
一次文献、二次文献、三次文献是按照( )进行区分的。

(本题4.0分)
A、加工深度
B、原创的层次
C、印刷的次数
D、评论的次数

参考答案：

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