What are the two sources or heat in earth's interior?

A) radioactive decay and convection currents

B) magma and liquid outer core

C) sunlight and meteor impacts

D) leftover heat from formation and radioactive decay

The flow of heat from Earth's interiorto the surface is estimated at terawatts (TW) and comes from two main sources in roughly equal amounts: the radiogenic heatproduced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of the Earth.