The project manager should call for a team meeting to identify the root cause for the declining performance, as this is part of managing project team. Managing project team involves tracking team member performance, providing feedback, resolving issues, and managing team changes. By calling for a team meeting, the project manager can engage the team members in problem-solving, address any conflicts or misunderstandings, and motivate them to improve their performance. The other options are not the best ways to improve the situation, as they either ignore, delay, or bypass the team involvement. References: (Professional in Business Analysis Reference Materials source and documents)

PMBOK Guide, 6th edition, Chapter 9, Section 9.4

PMP Exam Content Outline, June 2019, Domain III, Task 10

PMP Sample Test Questions, Question 175