Final answer:
The business agent of a craft union controls the union hall, while the president of an industrial union has a different focus.
Step-by-step explanation:
A feature that distinguishes the business agent of a craft union from the president of an industrial union is that he/she __controls the Union__ hall.
In a craft union, the business agent is responsible for managing the union hall, which serves as the central meeting place for union members. The agent is in charge of organizing meetings, maintaining the hall, and ensuring it is a functional space for members to gather.
On the other hand, the president of an industrial union focuses more on the overall leadership and representation of the union. While they may interact with the union hall, their role is not centered around directly controlling or managing it.