What does the following line suggest about the narrator's point of view?

"My heart grew sick; it was the dampness of the catacombs that made it so." (Paragraph 89)

A. The statement suggests emotional turmoil or a moment of remorse.
B. The statement reveals the effect the cold, damp area has on the narrator's heart.
C. The statement suggests that the narrator is not a cold-blooded killer but a person suffering from heart issues.
D. The statement reveals the effect that sweating while working in a cold area has on the mental state of the narrator.