According to the PMBOK Guide, a Scrum team is a self-organizing, cross-functional team that delivers value in short iterations called sprints. A burndown chart is a graphical representation of the work remaining versus time. An impediment is anything that prevents the team from achieving its sprint goal. The project manager, or Scrum Master, is responsible for facilitating the Scrum process and removing impediments that hinder the team's progress and performance. The project manager should take two actions to manage impediments and improve the team's velocity when a burndown chart indicates that the project is behind schedule. The first action is to look for processes that cause bottlenecks and slow down the team's agility. This will help to identify and eliminate any unnecessary or inefficient steps, rules, or procedures that hamper the team's ability to deliver value quickly and effectively. The second action is to work with the team to remove impediments as quickly as possible. This will help to resolve any issues, risks, or conflicts that affect the team's work, and to provide any support, guidance, or resources that the team needs to complete their tasks. Looking for processes that cause bottlenecks and slow down the team's agility and working with the team to remove impediments as quickly as possible are the two best actions that the project manager should take in this situation. Assigning the items with high complexity to senior developers (B) may not be optimal or fair, as it may create an imbalance in the team's workload, skills, and collaboration. Empowering the team to make decisions to remove impediments may be a good practice, but not an action that the project manager should take, as it is part of the team's self-organization and autonomy. Moving the items with high complexity to the last iterations (E) may not be feasible or advisable, as it may increase the project risk, scope creep, and technical debt. References: PMBOK Guide, 6th edition, pages 18, 177-178, 541-542.D