Answer:
The answer should be A. Adding carbon to iron makes it tougher and stronger.
The addition of carbon atom to iron metal, enhances the property of hardness of metal.
Alloy is a compound which is formed by the mixture of two or more than two metals with different properties to make a new compound with better properties.
When we add carbon atom in the iron metal, it deviates the crystal lattice property of iron and makes it more harder. So, the content of carbon in the iron is directly proportional to the hardness of iron metal.
Hence, option (A) is correct i.e. hardness.
To know more about hardness, visit the below link:
https://brainly.com/question/18173707
