Which arterial blood gas result reflects respiratory acidosis?

pH 7.48, PaCO2 37 mm Hg, HCO3 30 mEq/L

pH 7.28, PaCO2 31 mm Hg, HCO3 20 mEq/L

pH 7.39, PaCO2 38 mm Hg. HCO3 23 mEq/L

pH 7.30, PaCO2 50 mm Hg, HCO3 24 mEq/L