This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nuclear medicine, Subject name: Radiology
Which one of the following is NOT true concerning Radon? 
Select and explain. 
A. Decays by gamma emission, B. Single largest contributor to an individual's background radiation dose, C. Most stable isotope, 222Rn, has a half-life of 3.8 days, D. Implicated in Lung cancer
A: Decays by gamma emission
Answer: A: Decays by gamma emission 
Explanation: Radon Radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Often the single largest contributor to an individual's background radiation dose Radon continues to decay to emit alpha paicles. Rn-222 represents a long-term hazard despite its sho half life of 3.8 days.