The lines "Sometimes I growl, shake myself and spatter a few red drops for history to remember. Then—I forget." convey a more complex emotional response, but the imagery of "growl" and "spatter a few red drops" suggests a sense of agitation and perhaps even violence, which can create an angry tone. The use of the word "forget" contrasts with the intensity of the first part, indicating a cyclical nature of struggle that can leave the speaker feeling frustrated or resigned. Therefore, the most fitting response would be:
It contributes to an angry tone.