Correct Answer: Ocean

Solution : The correct answer is ocean.

The ocean or marine ecosystem is the largest ecosystem in the world and it is the most stable ecosystem. Water covers nearly 71% of the earth's surface area. While ecosystem is a self sustaining unit of interacting living organisms and their environment. It consists of all the biotic and abiotic factors. Ocean ecosystem is considered to be more stable as compared to other terrestrial ecosystems because terrestrial ecosystems undergo changes in the form of evolution. But the pace of such change in ocean ecosystem is very low.