The correct answer is D. Ocean.
Oceans are the most stable ecosystems on Earth. They cover over 70% of the planet’s surface and contain over 97% of the Earth’s water. The ocean is home to a vast array of life, including fish, coral reefs, and plankton. The ocean is also a major source of food and oxygen for humans.
Forests are also relatively stable ecosystems. They are home to a variety of plants and animals, and they play an important role in the Earth’s climate. However, forests are more susceptible to changes in climate than oceans.
Mountains are less stable ecosystems than forests or oceans. They are home to a variety of plants and animals, but they are also more susceptible to changes in climate and human activity.
Deserts are the least stable ecosystems on Earth. They are home to a variety of plants and animals, but they are also very sensitive to changes in climate and human activity.
In conclusion, the ocean is the most stable ecosystem on Earth. It is home to a vast array of life, and it plays an important role in the Earth’s climate.