Answer:
C. copper.
Explanation:
It is oxidation sate is changed from (+5) in the reactants (NO₃⁻) to (+4) in the products (NO₂). N gains 1 electron
So, it is reduced.
It is oxidation sate is the same (-2) in the reactants (NO₃⁻) and (-2) in the products (NO₂).
So, it is neither be oxidized nor reduced.
It is oxidation sate is changed (0) in the reactants (Cu) to (+2) in the products (Cu²⁺). Cu loses 2 electrons.
So, it is oxidized.
It is oxidation sate is the same (+1) in the reactants (H⁺) and (+1) in the products (H₂O).
So, it is neither be oxidized nor reduced.