This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology in Relation to Reproduction, Subject name: Gynaecology & Obstetrics
[{'content': 'Antibody to cross placenta \nSelect and explain. \nA. IgA, B. IgG, C. IgE, D. IgM', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. (b) Ig GRef: Robbin's 9th ed. /198-199", 'role': 'assistant'}]