What type of fuel are coal, petrol, and natural gas?

Energy from wood must be extracted more efficiently through

Which of the following types of wood is considered unfit for use as fuel?

Observe the figures $A$ and $B$ given below and answer the following questions.
$(i)$ The power generation by the above two methods is non-polluting. True/False.
$(ii)$ List any two applications of solar energy.
$(iii)$ What is a photovoltaic cell?

The current consumption of domestic firewood in India is about:

Which type of wood burns for a short period of time?