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': 'The commonest chromosomal abnormality in early spontaneous aboions is : \nSelect and explain. \nA. Monosomy, B. Autosomal trisomy, C. Triploidy, D. Tetraploidy', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Autosomal trisomy', 'role': 'assistant'}]