What is the main role of a stock broker?

The main role of a stock broker is to buy and sell securities on a stock exchange on behalf of clients. Stock brokers act as intermediaries between buyers and sellers in the stock market, executing trades according to the instructions of their clients. They have the expertise and access to market information necessary to facilitate these transactions efficiently. This role is foundational to the functioning of financial markets, as brokers enable individuals and institutions to invest in stocks, bonds, and other securities.

While the other options may involve financial services, they do not accurately capture the primary function of a stock broker. Personal financial advisors focus on providing comprehensive financial planning and advice, which is different from the transactional role of a broker. Managing real estate investments and negotiating loans are specialized professions that do not pertain to the stock market transactions that brokers handle. Thus, the focus on trading securities establishes why buying and selling on behalf of clients is the correct answer.