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: Gynaecology & Obstetrics
[{'content': "Implantation bleeding is called : \nSelect and explain. \nA. Haman's sign, B. Arias stella's sign, C. Hoffman's sign, D. Reinz's sign", 'role': 'user'}, {'content': "Answer: A \nExplanation: Haman's sign", 'role': 'assistant'}]