C
http://education.seattlepi.com/planet-gives-off-2-times-much-heat-receives-sun-5420.html
Explanation:
The orbit of the planet is considered to be stable and does not change over time. This means that the force of gravity and inertia are perfectly balanced. Leading to forward motion of Planet and moons under force of gravity of some other large body(Most probably stars).This is in turns leads to formation of orbit.
