According to the PMBOK Guide, the project manager should use appropriate conflict resolution techniques to manage conflicts among project stakeholders. One of the techniques is collaborating/problem-solving, which involves finding a mutually beneficial solution that satisfies all parties. This technique requires a high level of trust and cooperation, and may involve a face-to-face meeting to discuss the issues and options. The other options are either too passive, too formal, or too premature for resolving the conflict. References: PMBOK Guide, 7th edition, page 157-158, section 8.3.2.2.