The correct answer is (b) Sun.
Explanation: The Sun is considered the ultimate source of energy on Earth because all life forms ultimately derive their energy from the sun through photosynthesis. Plants use sunlight to create energy, which is then passed up the food chain to animals. Even fossil fuels, like coal and oil, are derived from ancient plants that captured solar energy through photosynthesis.
Why other options are incorrect:
(a) Water:
While water is a crucial component of many energy processes, it is not the ultimate source. Water’s energy is derived from the sun’s power driving the water cycle.
(c) Uranium:
Uranium is a radioactive element used in nuclear power plants to generate energy. However, the energy stored in uranium ultimately comes from the processes that formed it in the Earth’s core, which are not directly related to the sun’s energy.
(d) Fossil fuels:
Fossil fuels are derived from ancient organic matter that trapped the sun’s energy through photosynthesis. While they are a significant source of energy for humans today, the ultimate source remains the sun.