How does radioactivity make it possible to understand how Earth can be so old and still have a hot interior? (1 point)

A.Radioactive elements trap heat from underground magma chambers.
B.Radioactive elements absorb heat from the atmosphere and release it underground.***
C.Radioactive elements near the core release heat as their nuclei decay.
D.Radioactive elements absorb the cold temperatures underground.

3 answers

I don't agree with B.
http://www.thenakedscientists.com/forum/index.php?topic=35188.0
I'm also a little confused on this one.
Is it C, radioactive elemts near the core release heat as their nuclei decay?