Answer: D. supervisors gain experience in and are accountable for solving problems in their work units.
Step-by-step explanation:
A chain of command is necessary in business because it diversifies authority such that decisions can be made faster.
It works by dividing employees into units which will answer to a manager. That manager will make decisions for the unit and this leads to decisions being made faster because everybody wouldn't have to go to upper management when they already have a manager.
Supervisors/ managers of these units are therefore accountable for their units and will gain experience from being so.