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': 'Mechanism of IUCD includes all except: \nSelect and explain. \nA. Increase cervical mucus, B. Local foreign body like reaction, C. Decrease diameter of fallopian tube, D. Make Endometrium unourable for implantation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: MECHANISM OF ACTION IUDs Intrauterine device: Foreign body reaction in uterus Cellular and biochemical changes in Endometrium and uterine fluids. Impaired bility of gamete. Reduced chances of feilization. Copper ions (2nd generation) Alter biochemical composition of cervical mucus. Affect sperm motility/Capacitation / survival. Hormones (3rd generation) in IUD Increase cervical mucus viscosity, preventing sperm from entering cervix. Sustain unorable Endometrium for implantation by maintaining high level of progesterone.', 'role': 'assistant'}]