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
Which of the following is the most common illness leading to development of ARDS? 
Select and explain. 
A. Aspiration of gastric contents, B. Head trauma, C. Drug overdose, D. Bacterial pneumonia
D: Bacterial pneumonia
Answer: D: Bacterial pneumonia 
Explanation: Most cases (>80%) are caused by a relatively small number of clinical disorders: severe sepsis syndrome and/or bacterial pneumonia (~40-50%), trauma, multiple transfusions, aspiration of gastric contents, and drug overdose. Among patients with trauma, the most frequently repoed surgical conditions in ARDS are pulmonary contusion, multiple bone fractures, and chest wall trauma/flail chest, whereas head trauma, near-drowning, toxic inhalation, and burns are rare causes.Ref: Harrison 19e pg: 1736