Male Three-Spined Sticklebacks Occupy Inland Coastal Waters Where They Aggressively

Male three-spined sticklebacks occupy inland coastal waters where they aggressively defend their territories against intruding males.When tested with models of various shapes, sizes, and colors in the laboratory, males attacked crude models with red bellies more frequently than they attacked realistic models that lacked the characteristic red belly.These data suggest that

A) aggression is learned.
B) the red color of the male's underside is an unconditioned response.
C) the red color of the male's underside is a conditioned reflex.
D) the red color of the male's underside is a fixed action pattern.
E) the red color of the male's underside is a releaser for aggression.