The following sentences contain blanks. Use the drop-down menus to complete each blank correctly. The group of more than a thousand islands in the central and southern Pacific Ocean, known as [Dropdown 1] , includes the Hawaiian Islands, Samoa, and Tonga. These areas have an abundance of [Dropdown 2] , which formed as coral reefs that grew along the ocean floor. Other islands in this part of the world formed from volcanoes. Over time, a volcano eroded, leaving a ringlike island called [Dropdown 3] surrounding a lagoon.