This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Which of the following statements about twinning Is true? \nSelect and explain. \nA. The frequencies of monozygous and dizygous are the same, B. Division after formation of the embryonic disk result in conjoined twins, C. The incidence of monozygotic twinning varies with race, D. A dichorionic twin pregnancy always denotes dizygosity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Dizygotic twins arise from feilization of two Ova by different spermatozoa.Each twin has its own placenta,chorion and amnion. Monozygotic twins always result from splitting of a single feilised ovum and hence always of the same sex and look alike (refer pgno:178 sheila textbook of obstetrics 2 nd edition)', 'role': 'assistant'}]