Explanation
Lessons learned is a technique that involves identifying and documenting the knowledge gained from a project or an activity, and sharing it with relevant stakeholders. Lessons learned can include the successes, failures, best practices, and improvement opportunities that occurred during or after the project or activity. Lessons learned can help the BA to understand the stakeholders' level of satisfaction, to offer them an opportunity to help improve the working relationships, and to apply the learned knowledge to future projects or activities.
The other options are not the best techniques for this purpose, as they are more focused on identifying and managing risks, generating and evaluating ideas, or engaging stakeholders in a fun and creative way.
References: CBAP Handbook, CBAP Study Guide, BABOK Guide