Final answer:
A simple business structure is characterized by a flat organization, basic differences in work specialization, and low formalization.
Step-by-step explanation:
The characteristics of a simple business structure include flat organizational structure, very basic differences in work specialization, and low formalization. This organizational model is associated with small businesses and start-ups, where there are fewer layers of management, simpler job roles, and more flexible rules and procedures. In this context, the most correct answer is flat, very basic differences in work specialization, low formalization.