This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: RBC Development and Classification of Anemias, Subject name: Pathology
A 6-year-old girl is brought into the emergency room after an automobile accident. Physical examination shows bleeding from multiple wounds, and a CBC reveals a normocytic, normochromic anemia. Which of the following indices is most helpful in defining this patient's anemia as normocytic? 
Select and explain. 
A. Hematocrit, B. Hemoglobin, C. Mean corpuscular hemoglobin concentration, D. Mean corpuscular volume
D: Mean corpuscular volume
Answer: D: Mean corpuscular volume 
Explanation: - In this case scenario, MCV is most useful in determining anemia as normocytic, as it measures the average volume of red blood cells. - It categorizes RBCs by their average size. Normal range is 80-100 fl Cells with normal size are called normocytic smaller cells are termed microcytic larger cells are referred to as macrocytic MCHC: Measures average concentration of hemoglobin in a given volume of packed red cells.