This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Unit of radiation exposure ? 
Select and explain. 
A. Gray, B. Roentgen, C. Sieve, D. Red
B: Roentgen
Answer: B: Roentgen 
Explanation: Ans. is 'b' i.e., Roentgen Units of potency Roentgen and coulomb per kilograme - Units of exposure. It is the amount to which a person is exposed. Red and Gray- Units of absorbed dose. It is the amount which is absorbed per gram of tissue. Rem and Sieve - Product of the absorbed dose and the modifying factor. Represent the degree of potention danger to health