This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'Acute chest syndrome is caused by? \nSelect and explain. \nA. Sickle cell anemia, B. Pneumonia, C. Acute myocardial infarction, D. Penetrating chest tratuma', 'role': 'user'}, {'content': "Answer: A \nExplanation: Acute chest syndrome in sickle cell anemia is a distinctive manifestation characterised by chest pain,tachypnea,fever,cough,and aerial oxygen desaturation.It can mimic pneumonia,pulmonary embolism,bone marrow infarction and embolism,myocardial ischemia,or insitu lung infarction.Pulmonary infarction and pneumonia are the most frequent underlying or concomittant conditions in patients with this syndrome. Ref:Harrison's medicine-18th edition,page no:855.", 'role': 'assistant'}]