SAT Inferences Question

Ants and aphids are known to be mutualistic: ants feed on the honeydew produced by aphids, while aphids benefit from ants' protection against predators. If aphid colonies—which generally require relatively stable surfaces, such as trees or other woody plants, to thrive—are too small to produce significant volumes of honeydew, however, ants will prey on aphids. Researcher Tae-Sung Kwon examined ant and aphid abundance in two habitats in South Korea, one on the mainland and one on Jeju Island. Though the habitats differed in some important respects, both were predominantly grassland, which could help explain why Kwon observed Which choice most logically completes the text?