Question

Which of the following is a renewable source of energy
A. Natural gas
B. Coal
C. Petrol
D. Bio gas

Answer 1

Hint: Energy can neither be created nor destroyed. It is only converted from one form to another form. There are sources of energy. We use them to fulfil our daily needs. But if we keep on using them they will become extinct. These are called non renewable resources of energy. Definition of renewable sources is exactly opposite to the previous one.

Complete answer:
First if we talk about non renewable sources like coal and gas and petrol, we use them to get the required output. If we consider coal we heat it to get energy. If we consider locomotives in olden days, coal is used to heat the water in a boiler. The heated water will be converted into water vapor and that vapor will push the pistons which in turn connected to driving wheels. That means here the translatory motion of the piston is converted to the rotatory motion of the wheel. Same with present petrol and natural gas engines. The fuel will expand when burnt and cause the piston in the cylinder to move which in turn rotates the connecting rod and finally wheels will be rotated due to the transmission system in between.
So all these resources will become extinct if we keep on using them. But when we consider bio gas which is generated from human waste, it keeps on being created as long as bio waste is produced. Hence it is a renewable source of energy.

So the answer is option D.

Note:
Normally non renewable sources of energies are available under earth. But due to heavy excavation now they are available at less places than before. It takes several million years to form coal under earth. The rate of excavation is becoming very high. Very few years are left before all these non renewable sources become extinct.