The major processes that heat the interiors of the terrestrial worlds are:

a) (1) heat deposited as the planets were built from planetesimals; (2) heat of accretion; (3) heat that came from the gravitational potential energy of incoming planetesimals.

b) (1) heat of accretion; (2) heat from convection; (3) heat from thermal radiation.

c)(1) heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; (3) heat released by radioactive decay.

d)(1) volcanism; (2) tectonics; (3) erosion.