Which of the following does Rule 1.9 not explicitly address?

Rule 1.9 of the Model Rules of Professional Conduct specifically deals with the duties that a lawyer owes to former clients, particularly concerning conflicts of interest, the use of confidential information, and how these obligations affect a lawyer’s conduct when representing new clients.

The rule addresses conflicts with former clients by emphasizing that a lawyer must not represent a new client in a matter that is substantially related to the former client's matter, without the former client's informed consent. Additionally, it highlights improper use of confidential information gained during the previous representation, ensuring that such information is not used to the disadvantage of the former client.

However, Rule 1.9 does not explicitly address the nature of professional relationships with current clients. That topic falls primarily under Rule 1.7, which discusses conflicts of interest concerning current clients and the obligations lawyers have to them. Therefore, the choice regarding professional relationships with current clients is not covered by Rule 1.9, making it the correct response in this context.

The other options relate directly to the conflicts and duties a lawyer has concerning former clients, making them pertinent to Rule 1.9's primary focus.