The project manager should work with the team to analyze which processes are suitable to use and define them in the ground rules. This will help to resolve the conflict by creating a common understanding of the project processes, expectations, and norms among the team members from different companies. The project manager should also facilitate communication and collaboration among the team members and foster a positive team culture. Avoiding the conflict, reviewing the historical information, and asking the team to use company B's processes are not effective ways to resolve the conflict, as they do not address the root cause of the problem or involve the team in the decision-making process. References: = PMBOK Guide, 6th edition, pages 48-49, 343-344, 368-369; PMP Exam Content Outline, 2020, pages 6-7.