# The Axles are made by heating rods of iron embedded in charcoal powder . This process is known as

$(a)\;\text{Annealing} \\(b)\;\text{Tempering} \\(c)\;\text{case hardening } \\ (d)\;\text{Nitriding }$

The Axles are made by heating rods of iron embedded in charcoal powder . This process is known as case hardening
Hence c is the correct answer.

The answer is “C”, case hardening is also known as surface hardening used in making of Axles. This process is used to form a thin layer of harden metal that is called case. It is also used to harden element contents of bars that will be used for pattern welding.