A freshly prepared radioactive source of half-life 2 hours emits radiation of intensity which is...

A freshly prepared radioactive source of half-life 2 hours emits radiation of intensity which is 64 times the permissible safe level. The minimum times after which it would be possible to work safely with the source is ; (A) 6 hours (B) 12 hours (C) 24 hours (D) 128 hours 📲PW App Link - https://bit.ly/YTAI_PWAP 🌐PW Website - https://www.pw.live