Final answer:
A Scrum Master is most characteristically supportive, as they provide guidance and support to the team, facilitate Agile practices, and work to remove obstacles that impede the team's progress.
Step-by-step explanation:
The characteristic of a Scrum Master that best fits from the options provided is d. Supportive. A Scrum Master is not disengaged; rather, they are highly involved with the team, ensuring that everyone follows Agile practices. They are not solely task-focused, as their role is more about coaching and facilitating rather than managing tasks. They are process oriented, but this is not their only characteristic; they guide and support the team through the process. The most encompassing characteristic of a Scrum Master is being supportive, as they aid the team to become self-organizing, facilitate Agile practices, remove impediments, and help to improve the team's productivity and project outcomes.