Which of the Following Best Explains Why Many Jovian Moons

Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?

A) Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.
B) Because of their greater distances from the Sun, the jovian moons receive much less heat from the Sun.
C) The jovian moons are considerably larger than the Moon and Mercury and therefore have retained much more internal heat.
D) The jovian moons probably have far more internal heat generated by radioactive decay than do the Moon or Mercury.