Which of the following is considered a primary direct cost?

The selection of depreciation of vehicles as a primary direct cost is insightful in understanding how direct costs are classified in accounting. Primary direct costs are expenses that can be directly attributed to a specific project, product, or service.

Depreciation of vehicles falls under this category because vehicles are often used specifically for business operations, and their cost can be allocated directly to the products or services provided. When vehicles are used to deliver goods or services, the associated depreciation reflects the wear and tear directly linked to the revenue-generating activities of the business.

On the other hand, the other options, such as advertising expenses, personnel salaries, and utility bills, typically reflect more indirect costs. Advertising expenses might support overall brand efforts rather than a specific project, personnel salaries can cover employees whose roles are not solely dedicated to a single project, and utility bills are necessary for general operations rather than directly producible revenue. Thus, depreciation of vehicles stands out as a cost that can be directly traced to business activities, making it a primary direct cost.