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 most serious and life-threatening blood dyscrasias caused with a drug: 
Select and explain. 
A. Aplastic anemia, B. Megaloblastic anemia, C. Thrombocytopenia, D. Hemolytic anemia
A: Aplastic anemia
Answer: A: Aplastic anemia 
Explanation: None