This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Randomization means 
Select and explain. 
A. Mixing of cases and controls, B. Selecting cases, C. Selecting controls, D. Vaccine and Erythromycin
A: Mixing of cases and controls
Answer: A: Mixing of cases and controls 
Explanation: Randomization is a statistical procedure by which the study paicipants are allocated into groups usually called study and control groups; to receive or not receive an experimental preventive or therapeutic procedure, maneuver or intervention Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 90