The project manager should discuss the issue with the functional manager to understand the reason for the complaint. This is the best option because it shows the project manager's respect and communication skills, as well as the willingness to resolve the conflict in a constructive way. By discussing the issue with the functional manager, the project manager can also clarify the expectations, roles, and responsibilities of the team member, as well as identify the root cause and possible solutions for the problem. This option also aligns with the PMBOKGuide's guidance on managing stakeholder engagement, which includes addressing and resolving issues, and fostering collaboration among stakeholders1.
The other options are not as effective as option B. Option A is not fair and may demotivate the team member and the rest of the team. Option C is not collaborative and may escalate the conflict. Option D is not realistic and may create more interruptions and resistance from the functional manager. References: 1: PMBOK Guide, 6th edition, page 518