What unethical action did Mary commit while trying to sell Jane's house?

The action that Mary committed in this scenario involves disclosing confidential information. In real estate transactions, agents have a fiduciary duty to protect their clients' confidential information. This includes any personal data or property details that could influence negotiations or the sale's outcome. If Mary revealed information about Jane that she was obligated to keep confidential, it could undermine Jane's position in the sale and damage trust in the agent-client relationship.

While the other options detail potential unethical practices—such as dual agency without disclosure, attempting to profit from a net listing, or providing misleading information to buyers—they don't specifically address the violation of confidentiality. Protecting client information is fundamental to maintaining ethical standards in real estate and ensuring that clients can trust their agents to prioritize their interests.