阿摩線上測驗
30. If a sample of 
takes 62.7 days to decrease to 20.0% of its original mass, what is its half-life?
(A)0.0370 days
(B) 27.0 days
(C) 157 days
(D) 195 days
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統計： A(0), B(4), C(1), D(1), E(0) #2740203
統計： A(0), B(4), C(1), D(1), E(0) #2740203