Final answer:
The Iteration Review in Scrum, also known as the Sprint Review, should always be attended by the Product Owners and Developers. The Product Owners are responsible for the product backlog, while Developers provide details on the work and challenges.
Step-by-step explanation:
The question refers to the practices within Agile methodologies, specifically relating to Scrum, which is an iterative and incremental framework for managing complex work. An Iteration Review, more commonly referred to in Scrum as the Sprint Review, is a ceremony that occurs at the end of every iteration or Sprint. The purpose of this meeting is to inspect the increment of the product developed during the Sprint and to adjust the Product Backlog if needed.
According to Scrum guidelines, two groups that should always attend the Iteration Review are a) Product Owners and d) Developers. The Product Owner represents the stakeholders and is responsible for the product backlog, making sure that the development team delivers value to the business. The Developers are those who have worked on the product increment and can provide insight into the work completed and challenges faced. While c) Stakeholders may attend as well, it's not required that all stakeholders participate in every review. However, their feedback can be invaluable. The Scrum Master typically facilitates the meeting but is not one of the two groups mandated to be there.