This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'Which of the following events cause closure of ductus arteriosus in new born \nSelect and explain. \nA. Compression of thorax during delivery, B. Compression of pulmonary vessels during delivery, C. Fall in pulmonary arterial pressure, D. Fall in systemic arterial pressure', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Aeration of newborn lung causes rapid replacement of bronchial and alveolar fluid by air, with this compression of pulmonary vasculature is lowered which results in fall in pulmonary arterial blood pressure.\nThus ductus arteriosus closes.', 'role': 'assistant'}]