Which element is being reduced in this reaction?
#"H"_ 2"S"+ "HNO"_3 -> "S" + "NO" + "H"_ 2"O"#
Nitrogen is being reduced.
!! QUICK ANSWER !!
You can actually answer this question without balancing the chemical equation given to you.
All you need to notice here is that sulfur is paired with hydrogen on the reactants' side in hydrogen sulfide,
On the products' side, sulfur is present in its elemental form as
SIDE NOTE You'll often see elemental sulfur written as
So sulfur goes from a negative oxidation number to an oxidation number equal to zero
Now, hydrogen and oxygen almost always have oxidation numbers of
Therefore, option (C) is correct.
!! ANOTHER QUICK EXPLANATION !!
It's also very helpful to keep in mind that nitric acid,
This lets you know that in most reactions that feature nitric acid, you can expect this compound to oxidize another compound.
In this case, nitric acid oxidizes hydrogen sulfide to elemental sulfur,
Therefore, the answer will once again be (C)