How does the Tower Builder program ensure that Karel constructs a tower?

The program relies on repeatedly invoking the buildTower function to ensure that Karel successfully constructs a tower. This function contains the specific instructions that dictate how Karel interacts with the environment—typically involving placing a ball, moving up, and maintaining the necessary orientation to continue placing the next ball directly above the previous one. By continuously calling this function, Karel is able to execute the steps needed to add new balls one at a time, resulting in the desired tower structure.

While other options might suggest behaviors that could influence Karel's movements or the arrangement of the balls, they do not focus on the systematic process required to build a tower. Repeatedly calling the buildTower function encapsulates the entire sequence of actions necessary for tower construction within a single, effective cycle.