Which of the following blood workups would most likely demonstrate metabolic acidosis?
pH: 7.50; PCO2: 50 mmHg; HCO3-: 30 mEq/L
pH: 7.55; PCO2: 30 mmHg; HCO3-: 20 mEq/L
pH: 7.33; PCO2: 30 mmHg; HCO3-: 20 mEq/L
pH: 7.33; PCO2: 50 mmHg; HCO3-: 30 mEq/L