What practice was central to Semmelweis's contribution?

• A. Vaccination
• B. Sterilization of instruments
• C. Quarantine
• D. Handwashing

Answer: (D)

Hand hygiene to prevent infection transmission in clinical care is the key idea here. Semmelweis linked puerperal fever to contamination carried on physicians’ hands after they performed autopsies, then he required everyone to wash their hands with a chlorinated lime solution before delivering babies. This simple cleansing repeatedly cut maternal deaths, showing that removing infectious material from hands can stop the spread of disease in a hospital setting. Vaccination wasn’t a factor for puerperal fever at that time, quarantine doesn’t address transmission from professional to patient in this context, and while instrument sterilization is important in infection control, his major contribution was recognizing and enforcing handwashing as the critical barrier.