This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
In the following flow diagram, Box A represents: 
Select and explain. 
A. Metabolic alkalosis, B. Metabolic acidosis, C. Respiratory alkalosis, D. Respiratory acidosis
A: Metabolic alkalosis
Answer: A: Metabolic alkalosis 
Explanation: Metabolic alkalosis:
Metabolic alkalosis is characterised by an increase in the plasma bicarbonate concentration and the plasma pH. There is a compensatory rise in pCO2 due to hypoventilation, but this is limited by the need to avoid hypoxia. 
Classical causes include primary hyperaldosteronism (Conn’s syndrome), Cushing’s syndrome and glucocorticoid therapy. Occasionally, overuse of antacid salts for treatment of dyspepsia produces a similar pattern.