Final answer:
Henri Fayol is the management theorist responsible for the four functions of management: planning, organizing, leading, and controlling(OPTION 1).
Step-by-step explanation:
The management theorist responsible for what have become the four functions of management is 1) Henri Fayol.
Fayol is known for his work in defining the four functions of management, which are planning, organizing, leading, and controlling. He believed that these functions were essential for effective management and that managers should perform these functions to achieve organizational goals.
Fayol's ideas on management have had a significant influence on the field of business management and are still widely used today.