The correct answer is - A region composed mostly of islands.
Oceania is a region that is located in the Pacific Ocean. It is consisted of 14 island countries, and multiple other countries that are not fully independent and function as protectorats mainly of the USA and France. It is a vast region consisted of tens of thousands of islands, most of which are very small. The countries in this part of the world are very isolated and are mostly dependant on tourism and foreign aid to enable their existence. Also there's a new problem in the past few decades with the increasing level of the ocean waters, so some of the island countries, like Nauru for example, are losing their territory to the ocean, so it is very likely that in few decades will be totally submerged and not stop existing.