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: Pharmacology
A 30–year old epileptic female, Kamla on phenytoin therapy, developed weakness and fatigue. Blood examination revealed Hb = 4.6 gm. MCV = 102 fl and MCH = 40 pg/dl. What is the most probable diagnosis ? 
Select and explain. 
A. Heart failure, B. Iron deficiency anemia, C. Phenytoin induced agranulocytosis, D. Megaloblastic anemia
D: Megaloblastic anemia
Answer: D: Megaloblastic anemia 
Explanation: None