Which of the following is NOT one of the 3 marching steps used in drill?

The correct answer highlights that the 20-inch step is not one of the three standard marching steps used in drill. In military drill, the recognized marching steps typically include the 30-inch step, which is the standard for marching in formation, as well as the 15-inch step used for precision movements and the double time step, which corresponds to the 30-inch step at an accelerated pace.

The 20-inch step does not have a place in these established marching protocols. Understanding the different marching steps is essential for maintaining proper formation and execution during drills, ensuring that all personnel move cohesively. It is crucial to master the distinct purposes and applications of each of the recognized steps to achieve effective military discipline and order during drill exercises.