The correct answer is D. Atolls
Step-by-step explanation:
In geography, islands are small landmasses that are surrounded by water. Additionally, islands can be of man types including skerries cays or atolls. In the case of atolls, these are small islands composed by a coral reef or a sandy island over a coral reef that have the shape of a ring and therefore encircle an inner lagoon, this type of islands are the result of extinct volcanos and can be found on the Pacific Islands in which most islands are low-lying islands, which means islands do not have a high elevation from the sea and are island rings or atolls. Therefore, most low Pacific islands are rings of islands called atolls.