Question

one odd out
mountain, plateau, ocean​

Answer 1

Answer:

Ocean.

This is because mountain and plateau are not bodies of water.

Answer 2

$\implies \sf \: Ocean$

An ocean is a large area of water between continents. Oceans are very big and they join smaller seas together. Oceans (or marine biomes) cover 72% of our planet. It covers 1/3 of the Earth's surface. There are five main oceans together.