What are the two sources of thermal energy in earth's interior A: solar heating and gravity B: combustion and solar heating C: gravity and radioactive decay D: radioactive decay and combustion

The movement of heat from Earth's inner parts to the surface is approximately at 47 terawatts and comes from two major sources. These are the primordial heat left over from the Earth’s formation and the radiogenic heat caused by the radioactive decay of isotopes found in the mantle and crust. Earth's inner heat powers most ecological processes and handles plate tectonics. Despite its geological implication, this high temperature is coming from Earth’s inner part that is 0.03% of Earth’s total budget energy at the exterior that dominated by 173,000 terawatts of incoming solar radiation. the amount of solar radiation reaching a given area has eventually reached the surface after reflection into several tens of centimeters on the daily sequence and only various tens of meters on the yearly cycle. This provides solar radiation unrelated to inner processes.