Explanation
According to the PMBOK Guide, a scrum team is a cross-functional, self-organizing group of people who work together to deliver value to the customer in short iterations called sprints. A scrum team conducts daily meetings, also known as daily scrums or stand-ups, to synchronize their work, communicate progress, identify impediments, and plan the next steps. A daily meeting should be time-boxed to 15 minutes or less, and should focus on answering three questions: What did I do yesterday? What will I do today? What is blocking me? In this scenario, the project manager should train the three team leads to conduct a local meeting, then run an overall status meeting, as this can help to reduce the communication barriers, improve the efficiency and effectiveness of the meetings, and ensure the alignment and coordination of the three teams. Instructing the meeting participants to speak only about blockers, transferring half of the backlog items, or extending the meeting to 1 hour are not the best options, as they may not address the root cause of the problem, or may compromise the quality, scope, or schedule of the project. References: = PMBOK Guide, 7th edition, pages
14-15, 18-19, 22-23.