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: Anatomy
[{'content': 'Most commonest agent for Early Onset Nosocomial pneumonia is \nSelect and explain. \nA. Hemophilus, B. Staphylococcus aureus, C. Pseudomonas, D. Acinobacter', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Early Onset Nosocomial pneumonia which manifest within the first 4 days of hospitalization,is most often caused by community acquired pathogens such as Streptococcus pneumoniae and Hemophilus species Hospital-acquired pneumonia (HAP) or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48-72 hours after being admitted. It is thus distinguished from community-acquired pneumonia. It is usually caused by a bacterial infection, rather than a virus . Ref Harrison 19th edition pg 915', 'role': 'assistant'}]