Final answer:
HR strategies such as promotions, job rotations, and special assignments fall under management development, which is aimed at improving managerial skills. The widening gap between low-end and high-end jobs with fewer middle-level jobs is known as polarization. Scientific management's goal was to enhance workers' efficiency.
Step-by-step explanation:
The type of HR strategies that include promotions, job rotations, and special assignments are management development strategies. These strategies are aimed at improving the managerial skills and capabilities of employees to prepare them for higher-level positions. Management development helps individuals grow within the organization by enhancing their skills through a variety of learning opportunities.
Addressing another question, the practice where the differences between low-end and high-end jobs become greater and the number of people in the middle levels decrease is known as polarization. This phenomenon often arises due to technological advances and automation, which reduce the demand for middle-skill jobs while increasing demand for both high-skill and low-skill occupations.
Finally, the goal of scientific management was to increase workers' efficiency. This management theory, developed by Frederick Taylor, focused on the optimization of work processes and simplifying tasks to maximize productivity.