This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Least chances of pregnancy is with - \nSelect and explain. \nA. OCP, B. IUCD, C. Coitus interruptus, D. Condom', 'role': 'user'}, {'content': "Answer: A \nExplanation: park's textbook of preventive and social medicine 23rd edition. *Oral contraceptive of combined type are almost 100 effective in preventing pregnancy.some women do not take it regularly so the actual rate is lower.mechanis of action:prevent the release of ovum from ovary.this is achieved by blocking pituitary secretion of gonadotrophin.progestogen only preparation render the cervical mucous thick and scanty and there by inhibit sperm penetration.", 'role': 'assistant'}]