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.