This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fluids and Electrolyte Imbalance, Subject name: Medicine
pH= 7.30, pCO2= 38, HCO3 = 18, Diagnosis is? 
Select and explain. 
A. Metabolic acidosis with compensatory respiratory alkalosis, B. Respiratory acidosis with compensatory metabolic alkalosis, C. Respiratory alkalosis with compensatory metabolic acidosis, D. Metabolic acidosis with respiratory acidosis
D: Metabolic acidosis with respiratory acidosis
Answer: D: Metabolic acidosis with respiratory acidosis 
Explanation: Since pH is less, and HCO3 is less, it implies metabolic acidosis Now for compensation pCO2 = HCO3+ 15 = 18 + 15 = 33 The value predicted is not matching with given pCO2 of 38 mmHg. It implies compensation is not there and it is a mixed disorder. Conclusion metabolic acidosis with respiratory acidosis.