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: Pathology
Which of the following is the first symptom of iron deficiency anemia? September 2010 
Select and explain. 
A. Low iron concentration in blood, B. Reduced hemoglobin, C. Reduced PCV, D. Reduced ferritin
D: Reduced ferritin
Answer: D: Reduced ferritin 
Explanation: Ans. D: Reduced ferritin