1) What is combustion?
- A chemical process in which a substance reacts with oxygen to give off heat is called combustion

2) What are fuels?
- Substances that undergo combustion and produces heat energy are called fuels

4) Give examples for :-

a) Solid Fuels :- wood and coal
b) Liquid Fuels :- kerosene and diesel
c) Gaseous Fuels :- LPG (liquified petroleum gas) and CNG (compressed natural gas)