What is the primary purpose of a city-wide permit?

The primary purpose of a city-wide permit is to regulate construction activities. Such permits are essential for ensuring that all construction work complies with local building codes, zoning laws, and safety regulations. They serve to maintain order, safety, and community standards during construction projects. This process helps prevent issues such as unsafe building practices and zoning violations that could lead to public safety hazards.

The other options, while relevant in different contexts, do not align with the primary function of a city-wide permit. For example, notifying police departments and enabling public gatherings fall under different kinds of permits and regulations. Issuing fines for illegal activities is an enforcement measure rather than a primary purpose for obtaining permits. Thus, the correct option highlights the significance of permits in overseeing and controlling construction to safeguard community welfare.