This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pneumonia, Subject name: Medicine
[{'content': 'Recurrent aspiration pneumonia is caused by: \nSelect and explain. \nA. Dermatomyositis/polymyositis, B. Rheumatoid ahritis, C. Progressive systemic sclerosis, D. Systemic lupus erythematosus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Systemic sclerosis is characterized by fibrosis of lower esophageal sphincter | Leading to decrease in tone of LES | Resultant GERD | Leads to Recurrent Aspiration Pneumonia', 'role': 'assistant'}]