A Scrum Team must include both a Product Owner and a Scrum Master as they are fundamental roles in Scrum. These roles ensure that the team functions effectively and adheres to Scrum principles. The Product Owner is responsible for maximizing the value of the product resulting from the work of the Development Team, while the Scrum Master is responsible for promoting and supporting Scrum as defined in the Scrum Guide. Their participation and availability are critical as it directly impacts the outcomes produced by the Scrum Team.