Refer to the Following Reaction in Acid Solution

refer to the following reaction in acid solution.
CuS(s) + NO₃^-(aq) Cu²⁺(aq) + SO₄^2-(aq) + NO(g)
-In the balanced half-reaction for the NO₃^- ion, how many electrons are involved?

A) 1
B) 2
C) 3
D) 4
E) none of these