This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
First change of improvement, noted after iron therapy is initiated 
Select and explain. 
A. Decreased irritability, B. Reticulocytosis, C. Increase in serum iron levels, D. Replenishment of iron stores
A: Decreased irritability
Answer: A: Decreased irritability 
Explanation: 12-24 hr Replacement of intracellular iron enzymes; subjective improvement; decreased irritability; increased Appetite 36-48 hr Initial bone marrow response; erythroid hyperplasia 48-72 hr Reticulocytosis, peaking at 5-7 days 4-30 days Increase in hemoglobin level 1-3 mo Repletion of stores