According to the Scrum Guide, the Developers are accountable for managing the progress of work during a Sprint, as they are responsible for creating a valuable Increment that meets the Definition of Done and the Sprint Goal. The other options are not valid, as they imply that the Product Owner, the Scrum Master, or the most junior member of the team are accountable for managing the progress of work, which is not consistent with Scrum.

The correct answers are B and D, because the length of the Sprint should be chosen based on the level of uncertainty over the technology to be used and the risk of being disconnected from the stakeholders. The Scrum Guide states that "Sprints have consistent durations throughout a development effort. A new Sprint starts immediately after the conclusion of the previous Sprint. Sprints enable predictability by ensuring inspection and adaptation of progress toward a Sprint Goal at least every calendar month. When a Sprint's horizon is too long the Sprint Goal may become invalid, complexity may rise, and risk may increase."

A Scrum Master fulfills a different role than a traditional project manager, as stated in 2: "A project manager helps manage the project timeline, resources, and scope in order to meet business requirements. A Scrum Master, however, helps ensure the Scrum Team follows Scrum theory, practices, and rules. The Scrum Master is a servant-leader who helps optimize the value created by the Scrum Team."

The correct answer is E, because all of these topics can be discussed during a Sprint Retrospective. The Scrum Guide states that "the purpose of the Sprint Retrospective is to plan ways to increase quality and effectiveness.
... During each Sprint Retrospective, the Scrum Team plans ways to improve product quality by adapting the definition of 'Done' as appropriate." Therefore, the Scrum Team can discuss any aspect of their process, communication, skills, or definition of 'Done' that may help them improve.

According to the Scrum Guide 1 , the Sprint Backlog is the property of the Developers and no one else can tell them which items they should work on. The Developers can select any item from the Product Backlog that they forecast they can complete within a Sprint. The Developers are self-organizing and decide how to turn Product Backlog items into an Increment of value. Therefore, no one owns a Sprint Backlog item, but the entire Development Team is accountable for it.
References: Scrum Guide