A firm can develop its competitive advantage through its resources. Resources include:

a$.$ both the physical elements of production, such as machines and workforce, and the knowledge and expertise of how to make and sell a product or service.

b$.$ only inputs that are bought and sold on the open market at fair and reasonable prices.

c$.$ the competitors within an industry who seek to serve the same group of customers and serve the same customers' needs.

d$.$ the customers who choose to buy products or services from a company.