This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal circulation, Subject name: Gynaecology & Obstetrics
[{'content': 'All of these are responsible for preferential shunting of well oxygenated blood from fetal right atrium to left hea, EXCEPT? \nSelect and explain. \nA. Upper interatrial septum, B. Crista dividens, C. Pattern of blood flow in IVC, D. Size difference of left and right atrium', 'role': 'user'}, {'content': 'Answer: D \nExplanation: More oxygenated blood travels along the medial aspect of IVC and less along lateral aspect, facilitating shunting to opposite sides of hea, that is, more oxygenated travels to left hea through foramen ovale and less oxygenated to right ventricle. This is also facilitated by configuration of interatrial septum called crista dividens. So all are correct except option d.', 'role': 'assistant'}]