Question

Which of the following is the ultimate source of energy for all living organisms?
A. Food
B. Milk
C. Sun
D. Electricity

Answer 1

Hint: The very existence of living beings on earth requires an ‘unending' (renewable), ‘self-generated', and ‘powerful' source of energy to fulfill all the energy demands.

Complete answer:
The ultimate source of energy for all living organisms on earth is the ‘Sun’.
The Sun is an infinite and renewable source of energy which is also the most important source of energy for us. The energy from the sun is important for many processes such as photosynthesis, water cycle, nuclear energy, the formation of clouds, the formation of fossil fuels, etc. All our fossil fuels are derived from plants that existed millions of years ago. There are several resources to store the radiant energy of the sun. The most opt and common resource is the plants. Plants use the sun's radiant energy to produce food by photosynthesis and in return store the food (chemical energy) in their fruits, stems, and roots. This form of stored energy is also known as biomass energy. Biomass is a renewable source of energy.
In addition to direct solar energy from solar thermal sources, we can also utilize coal, oil, natural gas, biomass to procure energy. The wind and hydropower we harness to generate electricity originally derive their energy content from the sunlight only.

So, the correct answer is ‘Sun’.

Note: We can capture the thermal energy directly with the help of solar thermal panels that are made up of silicon and convert it into other forms. Alternatively, we can use photovoltaic (PV) cells, also called solar cells, to convert sunlight directly into electricity (‘photovoltaic’ essentially means ‘light electricity’).