Which answer would score higher? Not sure where to start? Explain this Answer A The half-life is 20 hours, so 60 hours contains two half-lives. The activity falls from 100% to 50% and then 25% of its initial value. Activity remains, so the isolated tool can still present a hazard. Answer B The half-life is 20 hours, so 60 hours contains three half-lives. The activity falls from 100% to 50%, then 25% and finally 12.5% of its initial value. Activity remains, so the isolated tool can still present a hazard.