Final answer:
An accelerating object must have a force acting on it, satisfying Newton's second law of motion. This force results in a change of velocity, which is the definition of acceleration.
Step-by-step explanation:
If an object is accelerating, it must be the case that a force is acting on the object. This is because acceleration is defined as a change in velocity over time, and according to Newton's second law of motion, a force must be applied to cause this change in velocity. Therefore, the answer to the question is B: The force is acting on the object.
It is important to note that acceleration does not necessarily imply that the object is a projectile or that it is falling due to gravity-—although these are specific scenarios where acceleration occurs due to gravitational force. An object in uniform circular motion also experiences acceleration because its direction is changing, even though its speed may be constant.
Furthermore, when a force is applied to an object on a smooth icy surface with zero friction, once the force stops, the object's acceleration becomes zero (Answer A); however, the object will continue moving at a constant speed. The parachutist mentioned in scenario 11 would stop accelerating when air resistance equals gravitational force, and move at a constant speed, not at an increasing or decreasing speed. Lastly, an object in projectile motion has an x-component of acceleration equal to 0 because gravity acts in the y-direction, not the x-direction.