Which two statements are the most accurate in regards to scaling Scrum for large projects requiring multiple Scrum Teams

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Which two statements are the most accurate in regards to scaling Scrum for large projects requiring multiple Scrum Teams? (Choose two.)

A. A person focusing on the Sprint Backlog of a single Scrum Team is often more productive than that same person working on multiple Scrum Teams at the same time.
B. A well-structured Product Backlog can minimize and often eliminate Development Team members working on multiple Scrum Teams during a Sprint.
C. Team members must work full time on a single Scrum Team.
D. Customizing the core Scrum framework is necessary to be successful with Scrum at large scale.