In the context of the history of American business, which of the following statements is true of the marketing era?

a$.$ Businesses focused on refining production processes and creating greater efficiencies.

b$.$ Businesses lost individual ownership as large factories emerged to increase production.

c$.$ Businesses began to develop brands to help customers understand the differences among various products.

d$.$ Businesses that dominated their markets ousted competitors, manipulated prices, and exploited workers.