Answer: C . The gravitational pull from Jupiter is much greater than any other forces acting on Io.
Step-by-step explanation:
Let's begin by the fact Jupiter is a huge massive planet, therefore the bodies that are closest to Jupiter will have a greater gravitational force than the other bodies. That is the situation with Io, the moon closest to Jupiter.
However, Io's orbit is very elliptical and eccentric compared to the outer moons, resulting in the distortion of its shape by the gravitational force. In fact, Io is considered the most geologically active object in the solar system, due to these variations.