A business owned by one person is called a(an):

A business owned by one person is referred to as a sole proprietorship because this structure is established when an individual operates a business independently, assuming full control and responsibility for all aspects of the operation. In a sole proprietorship, the owner retains all profits and bears all liabilities, which distinguishes it from other business structures where ownership is shared or divided.

Other options like partnerships involve two or more individuals sharing ownership and responsibility for the business, while corporations are separate legal entities that can own assets and incur liabilities independent of their owners. Cooperatives are organizations owned and operated for the benefit of a group of people. Thus, the defining characteristic of a sole proprietorship is the singular ownership, which makes it the correct answer in this context.