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: Microbiology
Simplest and most effective method to prevent nosocomial infection 
Select and explain. 
A. Use of antibiotics, B. Use of laminar airflow, C. Use of filters, D. Hand washing
D: Hand washing
Answer: D: Hand washing 
Explanation: As hand contact is the most common mode of transmission,
the best preventive measure of nosocomial infection is proper hand hygiene