Answer: d. the increasing fragmentation of the narrator’s sense of self.
The fragmented journal entries most likely symbolize the increasing fragmentation of the narrator's sense of self. As the narrator has been locked for so long, with no other way to stimulate her mind than that of her journal, this is likely to be the best account of how the narrator feels about her situation and about herself. As the journal becomes more fragmented, we can assume that the author is increasingly struggling to understand her own mind.