The Common Loon is a migratory bird that winters in warmer regions and returns to its breeding lakes in the spring. Typically, only one pair of loons occupies a single lake. Breeding pairs in search of breeding territory either occupy a vacant lake or take over an already occupied one. Surprisingly, almost half the time, returning loons choose to intrude on a territory already occupied by another pair of loons and attempt to oust its residents. This happens even when there are vacant lakes nearby that are perfectly suitable breeding territories. Which one of the following, if true, most helps to explain the surprising behavior described above? ['Loons that intrude on an occupied breeding territory are successful in ousting its residents about half the time.', 'Loons frequently determine that a lake is a suitable breeding territory by observing the presence of a breeding pair there.', 'Contests for occupied breeding territory may be initiated either by male loons or by female loons.', 'Lakes that are perfectly suitable for loon breeding have fish for food, a site for a nest, and a sheltered area to rear chicks.']