This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NCDs: CHD, HTN, DM, RF, Cancers, Obesity, Blindness, Subject name: Social & Preventive Medicine
MRFIT clinical trial for CHD was conducted in which country? 
Select and explain. 
A. USA, B. Finland, C. Norway, D. UK
A: USA
Answer: A: USA 
Explanation: - The Multiple Risk Factor Intervention Trial (MRFIT) was one of the coronary hea disease prevention trials recommended to the National Hea and Lung Institute in 1971 as an alternative to a national single-factor dietary trial, which was judged to be infeasible. - MRFIT carried out in USA was aimed at high risk adult males aged 35-57 years.