Explanation:

- The Pacific Ocean is the largest ocean on Earth, spanning more than 63 million square miles. It contains more water than all the Earth’s landmasses combined. This is why it gathers so much marine biodiversity and climatic influence.

- The Atlantic Ocean is the second-largest ocean, covering about 41 million square miles, known for its historical role in trade and exploration.

- The Indian Ocean ranks third in size. It is crucial for trade routes, with a vast expanse of roughly 27 million square miles.

- The Arctic Ocean is the smallest and shallowest, covering about 5 million square miles, and is mostly covered in ice.

Correct Answer: Option 2 - Pacific Ocean