Which substance acts as an oxidizing agent in the reaction $\text{Fe}+\text{S}\to \text{FeS}$?

Solution

1. The oxidation state of $\text{Fe}$ increases from $0$ to $+2$.
2. The oxidation state of $\text{S}$ decreases from $0$ to $-2$.
3. Since $\text{S}$ is reduced, it acts as the oxidizing agent.
4. Hence the answer is (B).