Types Of Extinguishers What Are The Basis Of Marking On The Portable Fire Fighting Extinguishers?

What are the basis of marking on the portable fire fighting extinguishers? - types of extinguishers

What is the reason for the following characters
i) triangle fire extinguisher to fight a fire-type
ii) Location of fire extinguishers to fight fires, types B
iii) The circle of fire extinguishers to fight fires of the type C