What action must be taken when merging the highest quality category with the next lower category?

When merging the highest quality category with the next lower category, the correct action is to list qualified preference eligibles at the top. This practice aligns with the principles of merit promotion and veterans' preference outlined in federal hiring regulations. By prioritizing qualified preference eligibles, the process ensures that candidates who have served in the military and meet the qualifications for the position are given the appropriate consideration in the selection process.

This prioritization of preference eligibles reflects the legal obligations to honor veterans' status, enhancing fairness in the hiring process. Acknowledging preference eligibles not only fulfills a commitment to veterans but also adheres to best practices in promoting equity in federal employment opportunities.

The other choices, although plausible in different contexts, do not align with the established protocols meant to support qualified preference eligibles.