This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Natural Methods, Barrier Methods, IUDs, OCPs, Subject name: Social & Preventive Medicine
[{'content': 'The most effective contraceptive available is: \nSelect and explain. \nA. Combined Oral contraceptive pill, B. Progestin injectable, C. Third generation IUCD, D. Centchroman', 'role': 'user'}, {'content': 'Answer: C \nExplanation: - Amongst the choices, third generation is most effective with a failure rate of only 0.2/HWY. PEARL INDEX OF DIFFERENT CONTRACEPTIONS: Male condoms 2-14 / HWY Female condoms 5-21 / HWY Centchroman 1.84 - 2.84 /HWY OCPs 0.1 - 2 /HWY Sterilization 0.1 / HWY Vaginal sponge 9-20 / HWY', 'role': 'assistant'}]