From the onset of the story, Rainsford is characterized as an experienced hunter who feels no remorse.
The difference between all the other choices and this one is that in the other options Rainsford is doing the characterizing. A character cannot characterize himself. The author is the one who is doing the characterization of his/her characters. The definition of characterization is the way the author presents the characters to the reader through their actions, thoughts, looks, speech and/or effects on others.