1) The word "island" contains two vowels: I and A.

2) The concept of quantum computing explores the use of quantum mechanics principles to perform complex computations, potentially revolutionizing fields such as cryptography and optimization.

3) The Arctic Ocean is the smallest and shallowest ocean, located at the North Pole. It is covered by sea ice for much of the year.

4) The Great Barrier Reef in Australia is the largest coral reef system in the world and is visible from space.