Which arterial blood gas result is most likely to result from renal failure?

pH 7.31, HCO3- 18 mEq/L, PaCO2 32 mm Hg

pH 7.29, HCO3- 25 mEq/L, PaCO2 51 mm Hg

pH 7.48, HCO3- 19 mEq/L, PaCO2 28 mm Hg

pH 7.52, HCO3- 28 mEq/L, PaCO2 36 mm Hg