C

Step 1: Analyze the first case (i), involving a mass released from a compressed spring. The graph for this situation will show that as the spring is released, potential energy decreases while kinetic energy increases, peaking when the mass is at its equilibrium position. Eventually, the potential energy is highest when the spring is fully compressed or extended.
Step 2: For the second case (ii), describing an object falling at terminal velocity, the potential energy decreases while kinetic energy stabilizes at a constant value, as the forces of gravity and drag are balanced. Thus, the total energy remains constant over time.
Step 3: In case (iii), an object undergoing free fall will show continually decreasing potential energy and increasing kinetic energy until reaching maximum velocity before hitting the ground, indicating a continual conversion of potential to kinetic energy.
Step 4: For case (iv), an object on a frictionless surface will show constant kinetic energy as it’s acted upon by a continuous external force, resulting in a linear increase of kinetic energy over time while potential energy remains constant.
Therefore, the correct match for the third graph aligns best with case (iii) of an object in free fall.