19. The radioactive nuclide of a certain element has undergone 87.5% decay during 360 years, which means that 12.5% of the original amount remains. How long is the half-life of this nuclide?
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(A) 180
(B) 150
(C) 120
(D)100 

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統計： A(1), B(0), C(0), D(0), E(0) #2818085