The half life of radioactive Radon is 3.8 days. The time at the end of which \[1/{{20}^{th}}\]of the Radon sample will remain undecayed is (Given\[{{\log }_{10}}e=0.4343\]) [IIT 1981]

• A.            3.8 days                                 
• B.            16.5 days
• C.            33 days                                   
• D.            76 days