Final answer:
A person negotiating sales of businesses for a fee (Option B) must have a real estate broker's license; other listed individuals manage their own property or act under specific grants of authority not requiring licensure. The correct option is B.
Step-by-step explanation:
Among the options provided, the individual that must have a real estate broker's license to lawfully transact business is B. A person who negotiates the sales of entire businesses, including their stock, equipment, and buildings, for a promised fee.
This activity falls squarely within the realm of professional real estate brokerage, as it involves negotiating on behalf of others for a fee, which typically requires licensure.
Conversely, option A, the owner who manages their own building, option C, the superintendent who shows apartments as part of their duties.
And option D, a person with written authority from parents to negotiate the sale of their residence, do not require a broker's license as they are either performing duties within the scope of property management or acting under a specific familial grant of authority. The correct option is B.