Many Seychelles warblers of breeding age forgo breeding, remaining instead with their parents and helping to raise their own siblings. This behavior, called cooperative breeding, results from the scarcity of nesting territory for the birds on the tiny island that, until recently, was home to the world' s population of Seychelles warblers. Yet when healthy warblers were transplanted to a much larger neighboring island as part of an experiment, most of those warblers maintained a pattern of cooperative breeding. Which one of the following, if true, most helps to explain the result of the experiment? ['Most of the terrain on the neighboring island was not of the type in which Seychelles warblers generally build their nests.', 'Cooperative breeding in species other than the Seychelles warbler often results when the environment cannot sustain a rise in the population.', "The climate of the island to which Seychelles warblers were transplanted was the same as that of the warblers' native island.", 'The Seychelles warblers had fewer competitors for nesting territory on the island to which they were transplanted than on their native island.']