You have been assigned as the project manager using Agile Project Management with a team of twelve. You seek to identify project roles and distinguish key responsibilities for project team members. Which best describes the role of Scrum Master:

a$.$ The person who facilitates and guides the team to improve performance, removing roadblocks, so the members can focus on their work

b$.$ A person who works on a project in cooperation with others to develop the solution for the stakeholder.

c$.$ The person who represents the client or customer and other stakeholders, prioritizing work and making timely decisions, enabling an Agile project team.

d$.$ The person who approves the budget and schedule changes.