The correct answer is: A. ongoing cost.
Overhead is a cost that is incurred in the course of business operations and cannot be directly attributed to a specific product or service. It is an ongoing cost that must be paid regardless of the level of production or sales. Some examples of overhead costs include rent, utilities, insurance, and salaries for administrative staff.
Option B, basic cost, is incorrect because overhead is not a basic cost. It is a cost that is incurred in addition to the basic costs of production or sales.
Option C, extra cost, is incorrect because overhead is not an extra cost. It is a cost that is necessary to operate a business.
Option D, chargeable expenses, is incorrect because overhead is not a chargeable expense. It is a cost that is not directly attributable to a specific product or service and therefore cannot be charged to customers.