A satellite S S\,S is in a stable circular orbit around Earth EEE, moving at a constant speed.
Why does the velocity of S S\,S change?
An unbalanced gravitational force acts on SSS at right angles to its velocity.
The forces acting on SSS are completely balanced.
The gravitational pull of SSS on Earth is greater than that of Earth on SSS.
There is a resistive force in space acting in the direction of the orbit.