A. It is an old concept and overall not recommended.
B. It helps the Product Owner to decide when the product is releasable.
C. It gives an overall direction to all Sprints, makes it easier to prioritize Product Backlog items and
helps the team to stay focused.
Explanation:
The "Product Vision" is not part of the Scrum Guide but a very recommended concept that is also promoted by Scrum. org.