Concept:An industry is a collection of firms that make products which are closely linked to one another.
Explanation:In economics, an industry refers to a group of firms operating in the same line of production.
These firms produce goods that are related in nature, such as the many companies that manufacture vehicles in the automobile industry.
The products sold by these firms are sometimes identical, or they may be close substitutes for each other.
Each firm in the industry is often separately owned and controlled, yet they still fall under the same industry because of their related output.
Thus, the essential idea is that the commodities produced are related, not differentiated, distinct, or entirely unrelated.
Answer: C. A group of firms producing related goods