Final answer:
Products may be differentiated in all of the following ways EXCEPT location. Therefore, the correct option is C. location.
Step-by-step explanation:
A firm can differentiate its products in several ways, such as physical characteristics, method of production, location, and convenience. However, one way that products cannot be differentiated is by their location. Differentiation based on physical characteristics refers to attributes like size, color, design, or features. Method of production refers to the process used to create the product, such as handmade or mass-produced. Convenience refers to aspects like accessibility or ease of use. Therefore, the correct answer is C. location.