The phrase which best defines "author's perspective is the following one:
c.)the author's attitude toward and opinion about the topic.
We are talking about a perspective, that is, a point of view or a subjective evaluation. Therefore, nothing can be more subjective than one's attitude and opinion about a particular topic, since every individual is entitled to his or her opinion. In other words, everyone has got a perspective of their own, and that includes writers, whose personal impressions and judgement can be sensed in their works, sometimes very clearly, sometimes between the lines.