Carbon-14 is a radioactive isotope. It is found in the air in carbon dioxide molecules. The amount of carbon-14 in the air has stayed the same for thousands of years. There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain.

Once an organism dies, it stops taking in carbon-14. The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.

The approximate time since the organism died can be worked out by measuring the amount of carbon-14 left in its remains compared to the amount in living organisms.

In 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain. Small samples from his body were carbon dated by scientists and found to contain 50% carbon-14 remaining. Based on this finding, how old are the remains of the body estimated to be?

A.
About 5,700 years

B.
About 11,400 years

C.
About 22,800 years

D.
Over 30,000 years