Answer is A (Respiratory acidosis with compensatory metabolic alkalosis) Because primary respiratory component is causing acidosis and metabolic component is compensatory by producing alkaosis, the acid base disorder is Respiratory acidosis with compensatory metabolic alkalosis. STEP 1 : What is the pH. Normal pH pH of patient Inference Is it acidosis or alkalosis 7.35 - 7.45 7.2 Decreased pH Acidosis STEP II : What component is primary and what is compensatory Parameter Inference Is change towards acidosis or alkalosis Is change in keeping with change in pH Final Inference pCO3 = 50mm Hg increased acidosis Yes Primary component is (Respiratory component) (pH=7.2 = Acidosis) respiratory (acidosis) HCO3- = 32 mmHg increased Alkalosis No Metabolic component is (metabolic component) (pH=7.2 = Acidosis) compensatory (alkalotic) STEP III : Final deduction Because the primary component is respiratory and the metabolic component is compensatory the acid base disorder is respiratory acidosis with compensatory metabolic alkalosis.