This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Most common cause of the first-trimester aboion is \nSelect and explain. \nA. Chromosomal anomalies, B. Infections, C. Rh incompatibilty, D. Cervical incompetence', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Causes of 1st trimester aboion : Genetic factors -50% Endocrine disorders Immunological disorders Infection Unexplained Ref: Dutta Obs 9e pg 153.', 'role': 'assistant'}]