Fact 1: Aggression is behavior that is intended to cause harm or pain. Fact 2: Also, pain is an excellent deterrent. Given the two facts above, what can be a deterrent?

Pick from:
(a). sunlight;
(b). fur seals;
(c). crocodiles;
(d). change;
(e). tail fins;
(f). aggression;
(g). herbicide;
(h). hope;
The answer is:
(f).