It is the Sun itself which sends energy in the form of heat and light, and these energies vary according to the Sun's position relative to the Earth.
(the Sun; sends; energy) (It; is; the Sun) Context(It is,List([0, 5))):(these energies; vary; according to the Sun's position relative to the Earth)
It is,List([0, 5))
the Sun It these energies
sends is vary
energy
the Sun
according to the Sun's position relative to the Earth