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': 'Most common abnormality for 1st trimester aboion is : \nSelect and explain. \nA. Trauma, B. Placental and membrane abnormalities, C. Chromosomal abnormalities/ Germ plasm de fect, D. Retroversion', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Chromosomal abnormalities/ Germ plasm de fect', 'role': 'assistant'}]