Which of the following is a behavioral pattern resulting from an ultimate cause?
A) A male robin attacks a red tennis ball because it resembles the breast of another male.
B) A male robin attacks a red tennis ball because hormonal changes in spring increase its aggression.
C) A male robin attacks a red tennis ball because a part of its brain is stimulated by red objects.
D) A male robin attacks a red tennis ball because several times in the past red tennis balls have been thrown at it, and it has learned that they are dangerous.
E) A male robin attacks a red tennis ball because it confuses it with an encroaching male who will steal his territory.
Answer: E