Question

an island is a piece of land that is fully surrounded by water.
select the island.

Explanation:

To determine the island, we use the definition: an island is land fully surrounded by water. The first image shows a landmass completely surrounded by water. The second has a landmass connected (a peninsula - like structure, not fully surrounded), and the third is a coastal or mountainous area connected to a larger landmass (not an island). So the first image is the island.

Answer:

The first image (the one with the circular - shaped landmass fully surrounded by blue water) is the island.