What ethical duty may have been violated if you sold speculative stocks without knowing the customer's risk tolerance?

The ethical duty that may have been violated in this scenario is the duty to diagnose. This duty emphasizes the importance of understanding a client’s financial situation, risk tolerance, and investment goals before making recommendations. Selling speculative stocks without knowing the customer's risk tolerance indicates a failure to assess the client's needs and understanding of risk, which is critical for responsible investment advice.

A financial professional must diagnose a client's circumstances accurately to align investment choices with their capacity for risk and their overall financial strategy. Engaging in transactions without this understanding can lead to mismatched investments that may harm the client's financial wellbeing.

Other options, while important, do not fully capture the ethical responsibility required in this situation. The duty to inform relates to providing relevant information to clients, the duty of confidentiality pertains to safeguarding a client’s personal information, and the duty to execute deals with the obligations of fulfilling trade orders properly. However, they do not address the fundamental need to understand a client's risk profile, which is at the forefront of making suitable investment decisions.