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: Medicine
After how many hours of hospital admission does nosocomial infection occur? 
Select and explain. 
A. 24 hours, B. 36 hours, C. 48 hours, D. 72 hours
C: 48 hours
Answer: C: 48 hours 
Explanation: Nosocomial infections can be defined as those occurring within 48 hours of hospital admission, 3 days of discharge or 30 days of an operation. They affect 1 in 10 patients admitted to hospital.  Nosocomial comes from the Greek word nosokomeion meaning hospital (nosos = disease, komeo = to take care of ). This type of infection is also known as a hospital-acquired infection.