Taking into account the statement above: "Which of the following is included in the definition of underwriter, according to the Securities Act of 1933." and the set of options: A] Agents
[B] Investment Advisers (IA s)
[C] Issuers
[D] Broker-Dealers
The answer is: D.
The broker-dealers are included in the definition of underwriter since they underwrite new issues. Also, the Issuers are issuers, and do not underwrite their own issues. The Investment advisers are registered to give investment advice. So, the agents work for broker-dealers, but they are not included in the definition of underwriter.
Hope this helps.