Which choice most logically completes the text?

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The olona shrub is one of many forest plant species native to Oahu (a Hawaiian island) that are at risk of extinction in the wild. Ecologists say that fruit-eating birds help support these species' population numbers by dropping seeds from the plants' fruits to different spots where new plants can grow. The birds native to Oahu that used to do this have all gone extinct over time. However, the common waxbill and other fruit-eating bird species brought to the island in the last 150 years have been found to spread plant seeds. Based on this finding, some ecologists suggest that olona shrubs and other forest plants native to Oahu ______

probably established themselves on the island at about the same time as common waxbills and other fruit-eating birds did.

may now depend on non-native birds, such as the common waxbill, to help maintain and increase their populations on the island

were likely already close to extinction long before non-native birds arrived on the island

seem to produce fewer fruits per plant now than they did when fruit-eating birds native to the island were still present