Gold Does Not React with Either Nitric Acid or Hydrochloric

Gold does not react with either nitric acid or hydrochloric acid but with a combination of both called aqua regia.Identify the reducing agent in the following equation:
Au(s) + 4 H⁺(aq) + NO₃^-(aq) + 4 Cl^-(aq) → [AuCl₄]^-(aq) + 2 H₂O(l) + NO(g)

A) Au
B) H⁺
C) NO₃^-
D) Cl^-
E) Au and Cl^-