Which risk response involves using strategies like changing schedules or working procedures to diminish risk impact?

Mitigating is the correct choice because it relates to implementing actions designed to reduce the likelihood or impact of a risk. When a project manager identifies a risk, they may employ various strategies to bring the potential effect down to an acceptable level. This can include adjusting schedules, modifying work procedures, or introducing new policies that aim to minimize the risk's consequences on the project.

In this context, when specific steps are taken to reduce either the frequency with which the risk can occur or the severity of its impact should it occur, it clearly falls under mitigation. This strategy directly addresses the concern of managing risks actively rather than simply accepting them or transferring their responsibility to others.

Other risk response strategies, such as avoiding, retaining, or transferring, serve different purposes. Avoiding would mean changing plans to sidestep the risk entirely. Retaining would imply accepting the risk without attempts at reduction, whereas transferring generally involves shifting the impact of the risk to another party, such as through insurance. Each of these strategies has its own place in risk management but do not specifically focus on reducing risk impacts through adjustments to workflows or schedules as mitigation does.