All the following statements are true. Which one is most important in explaining the tremendous tidal heating that occurs on Io?

Jupiter has four large moons (IO, Europa, Callisto and Ganymede), out of these three moons are in an orbital resonance with it (IO, Europa and Ganymede). Among these, Io is the innermost one. The interactions of Jupiter and its other moons with IO maintain IO's orbit in an elliptical state.

Hence the distance between Jupiter and IO changes continuously with change in position of IO on its orbit. This change in distance causes a distortion of IO's shape and flexes its interior, due to tidal energy, as the part of IO closer to Jupiter experiences extremely large gravitational pull compared to the distant part.

These internal geological changes on IO frictionally heat it, and this heat induced due to friction causes very strong volcanic activities.