If we ignore friction and any other opposing forces, the object will continue moving at a constant speed due to Newton's First Law of Motion, which states that an object in motion stays in motion unless acted upon by a net external force.
Since there are no opposing forces to overcome (like friction), the amount of force required to keep the object in motion at a constant speed of 3.5 meters/second is 0 newtons.
So the correct answer is:
A. 0 newtons