Io maintains a constant orbit around Jupiter because
A
Io is held trapped within Jupiter's atmosphere due to friction caused by air resistance.

B
Io has been caught in the magnetic field created by Jupiter's rotation about its own axis.

C
the gravitational pull from Jupiter is much greater than any other forces acting on Io.

D
high pressures and gases cause reactions on Jupiter that pull Io toward the planet.

C . The gravitational pull from Jupiter is much greater than any other forces acting on Io.

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.

it will be pushed away from the source of the electric field. a negative charge in a cloud induces a positive charge in the ground below the cloud.

explanation:

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.