Final answer:
The required written agreement of broker-salesperson is a regulation of securities in the business field. It ensures that individuals involved in selling securities adhere to certain standards and practices.
Step-by-step explanation:
The required written agreement of broker-salesperson is a regulation of the business of securities. The regulation mentioned in the question refers to the oversight and supervision of the sale of securities by brokers, dealers, and bankers. This regulation ensures that the individuals involved in selling securities adhere to certain standards and practices, protecting both the investors and the integrity of the financial markets.