Answer: iron and carbon, stronger.
Explanation: Steel is an alloy made by mixing iron with small quantities of carbon.
Iron being a pure metal is malleable and brittle due to the presence of free electrons. The atoms of the metals can slip over one another due to these free electrons.
When carbon is added to iron, an alloy is formed and becomes hard as presence of carbon do not allow the atoms to move past one another. The tensile strength or resistance to break under applied force for steel gets more as compared to iron.
Thus steel is stronger as compared to iron.
