This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concept of health and disease, Subject name: Social & Preventive Medicine
Which of the following constitutes secondary prevention 
Select and explain. 
A. Health education programmes, B. Wearing safety helmets, C. Using limb calipers, D. Screening test
D: Screening test
Answer: D: Screening test 
Explanation: Secondary prevention includes early detection ( diagnostic tests and screening tests) and treatment. Ref: Park's textbook of preventive and social medicine; 23rd edition; Page no 42