Which of the following inhabitants of oceans is considered as the "rain forest of oceans"?

Explanation

The correct answer is Coral reefs. Coral reefs are known as the 'rain forests of the ocean' because they support a vast array of marine life, providing habitat, food, and breeding grounds for numerous species. They are crucial for biodiversity, much like the terrestrial rain forests. The other options, such as Hydra and jellyfish, do not provide the same level of ecological services or support such a wide variety of life forms. Sponges contribute to the ecosystem but do not create complex habitats like coral reefs do.