The correct answers are A and C. According to the PMBOK Guide, the five whys and the Ishikawa diagrams are examples of data analysis techniques that can be used to identify the root causes of problems or issues1. The project manager can use these tools to determine why stakeholder engagement is not having the planned effect and address the underlying factors. The communications management plan is a document that describes how project communications will be planned, managed, and controlled2, but it does not help to analyze the reasons for stakeholder engagement issues. The issue log is a project document that records and monitors the issues that arise during a project3, but it does not help to find the root causes of those issues. Open-space meetings are a type of interpersonal and team skills that can be used to facilitate stakeholder engagement and collaboration, but they do not help to diagnose the problem of stakeholder engagement. References: 1: PMBOK Guide, page 698; 2: PMBOK Guide, page 377; 3: PMBOK Guide, page 123; : PMBOK Guide, page 704