What are jobs for the Scrum Master in Scrum’s structure. (More than one answer)

A、Ensuring Scrum is understood and enacted.;
B、Ensuring that the Scrum Team adheres to Scrum theory, practices, and rules.;
C、The Scrum Master is a servant-leader for the Scrum Team.;
D、Helping those outside the Scrum Team understand which of their interactions with the Scrum Team are helpful and which aren’t.