Final answer:
A broker operating as a sole proprietorship under an assumed name is classified as a DBA ('Doing Business As').
Step-by-step explanation:
A broker who conducts business as a sole proprietorship under an assumed name is classified as a DBA ("Doing Business As"). This is one of the three forms of business organization in the United States; others include partnerships and corporations. In a sole proprietorship, the business is not a separate entity from the owner. The owner is responsible for all debts, and liabilities, and is entitled to all profits. This straightforward structure is often chosen for its simplicity, although the owner faces unlimited personal liability for business debts.