The proportion of carbon-14 in an organism is useful in figuring out the age of that organism after it dies because...?
A. carbon-14 decays to carbon-13.
B. the proportion of carbon-14 is stable forever.
C. carbon-14 becomes more plentiful over time.
D. the proportion of carbon-14 slowly decreases after the death of the organism.
E. It is not true that the proportion of carbon-14 is useful in dating the ages of organisms.