Answer: Option (a) is the correct answer.
Step-by-step explanation:
Metals are the substance which have excess of electrons. Therefore, they are good conductors of heat and electricity as they have mobile electrons.
Out of the given options, iron is a transition metal which are good conductors of heat and electricity.
Sulfur and carbon are non-metals, therefore, they are bad conductors of heat and electricity.
Tin is a poor metal so it will not conduct electricity effectively as compared to iron.
Thus, we can conclude that out of the given options, iron is likely to be the best conductor.