Question

Sun is the only source of energy for all the ecosystems on Earth, except

Answer 1

Sources of energy on Earth :
The ultimate source of energy on Earth is the Sun which is required for the production of food through the process of photosynthesis by the producers. This helps to maintain energy flow in the ecosystem through the food chain as producers are the ultimate sources of food for all living beings on earth.
Apart from the Sun, some deep sea hydrothermal vents also act as a source of energy. These vents discharge water which has been superheated by the geothermal energy beneath the earth’s crust that escapes through these vents. The ecosystems surrounding such hydrothermal vents are powered by this geothermal energy.

Final answer :
(C) Deep sea hydro-thermal ecosystems