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
Thromboembolism is due to which component of oral contraceptive pills: 
Select and explain. 
A. Progesterone, B. Estrogen, C. Iron, D. FSH
B: Estrogen
Answer: B: Estrogen 
Explanation: None