Resource-leveling is used when resource constraints such as labor, materials, or equipment availability might prevent schedule logic from being followed.
Option A references float-banking, unrelated to resource leveling.
Option C suggests never performing leveling unless required, which overlooks the need to address actual resource limitations.
Option D is incorrect as a resource-loaded schedule may still need leveling for optimization.
Resource management principles in the PSP Study Guide discuss when and why to apply resource leveling​​.