This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition and health, Subject name: Social & Preventive Medicine
Protein efficiency ratio is - 
Select and explain. 
A. Gain weight per unit of protein consumed, B. Product of digestibility coefficient and biological value divided by 100, C. Percentage of nitrogen retained out of the nitrogen absorbed, D. Percentage of protein absorbed after digestion
A: Gain weight per unit of protein consumed
Answer: A: Gain weight per unit of protein consumed 
Explanation: Protein efficiency ratio (PER) is based on the weight gain of a test subject divided by its intake of a paicular food protein during the test period. From 1919, until very recently, the PET has been a widely used method for evaluating the quality of protein in food Ref: Dictionary of public Health, Dr. Jugal Kishore Pgno : 423-424