In a functional organizational structure, departments such as purchasing operate independently and are managed by their respective department heads12. When project tasks are delayed due to other priorities within a department, it is essential for the project manager to engage directly with the department causing the delay- in this case, the purchasing department. By meeting with the purchasing manager, the project manager can discuss the importance of the project's tasks, understand the reasons for the delay, and work collaboratively to establish a purchasing schedule that aligns with the project's needs while respecting the department's constraints345. This approach fosters communication and collaboration, which are key in a functional structure where the project manager has limited authority over departmental resources.
= The role of the project manager in a functional organizational structure and the importance of direct communication with department heads to resolve delays and align schedules are well-documented in project management literature12345.

When stakeholders raise concerns despite receiving updates, it suggests there may be a gap in understanding or relevance of the information shared. The project manager should meet directly with those stakeholders to assess the root cause of their concerns and determine whether the plan-or the way it is communicated- needs to be adjusted.
According to the PMBOK Guide - Seventh Edition, effective stakeholder engagement involves not only communication but also actively understanding and addressing their expectations and concerns.
Option B is reactive and narrow in scope.
Option C is Agile-specific and doesn't fully apply if this is a traditional setting.
Option D assumes the communication method is the only issue rather than validating stakeholder input.
References:
PMBOK Guide - Seventh Edition, Stakeholder Performance Domain
PMI Practice Standard for Stakeholder Engagement