Which of these methods of heating a planet is least likely to decline over the lifetime of the Solar System?

Which of these methods of heating a planet is least likely to decline over the lifetime of the Solar System?

Which of these methods of heating a planet is least likely to decline over the lifetime of the Solar System?

a) Heating by accretion
c) Heating by the Sun
d) Heating by radioactive decay
e) Heating by gravitational contraction

C, the Sun

It will not burn like it does for ever. It will turn into a red giant and then back down to a white dwarf and then ultimately burn out.

Heating For Home

[SMP_MESSAGE]