Answer: a. A collection of firms that compete with one another in a single product market
Explanation: An industry would be defined as a collection of firms that compete with one another in a single product market. In other words, an industry consists of a group of businesses of the same type, considered as a whole, and consists of large-scale enterprises in a sector of the economy. These businesses are classed into industries based on the primary product produced or sold (major source of revenue).