Explanation
A) The stakeholders have not been using the Sprint Reviews to actively engage, and inspect and evaluate progress. This is a possible factor that may have led to the disappointment and anger of the stakeholders. The Sprint Review is an event where the Scrum Team and the stakeholders collaborate to inspect the product Increment and adapt the Product Backlog based on feedback and new insights. If the stakeholders do not participate actively in the Sprint Review, they may miss the opportunity to provide input, voice their concerns, and influence the direction of the product development.
D) The Scrum Master has not ensured transparency. This is another possible factor that may have led to the disappointment and anger of the stakeholders. The Scrum Master is accountable for establishing and promoting transparency among the Scrum Team and the stakeholders, by ensuring that everyone has a clear and common understanding of the product vision, the Product Goal, the Product Backlog, the Sprint Goal, the Sprint Backlog, and the Definition of Done. Without transparency, there may be misalignment, confusion, or unrealistic expectations among the stakeholders regarding the product being built.
E) The Product Owner has not been interacting frequently with the stakeholders and kept them aware of the progress of the project. This is also a possible factor that may have led to the disappointment and anger of the stakeholders. The Product Owner is responsible for engaging with the stakeholders regularly and communicating the value, scope, and status of the product development. The Product Owner should also seek feedback from the stakeholders and incorporate it into the Product Backlog refinement and ordering. If the Product Owner does not interact frequently with the stakeholders, they may feel disconnected, ignored, or dissatisfied with the product being built.
References:
The Scrum Guide, section 2.3 (The Scrum Team), page 7
The Scrum Guide, section 3.6 (The Sprint Review), page 11
The Scrum Guide, section 4.1 (The Product Backlog), page 11
The Scrum Master Learning Path, module 2 (The Scrum Framework), lesson 5 (The Sprint Review) and lesson 6 (The Sprint Retrospective)

Explanation
Using Scrum does not ensure that adding more resources to a project proportionally increases the value delivered. In fact, adding more resources may have the opposite effect, as it can introduce more complexity, communication overhead, coordination challenges, and integration issues12. Scrum values quality over quantity, and focuses on delivering the most valuable and feasible outcomes in a given timebox3 . Scrum also encourages teams to be self-organizing and cross-functional, which means that they can work autonomously and collaboratively without relying on external resources or dependencies3 .
References: 1: Adding more resources in Scrum will proportionally increase the value ... 2: The Mythical Man-Month - Wikipedia 3: Scrum - What is it, how it works, & how to start - Atlassian : How Scrum Teams can Complement Scrum by Adding Practices, Tools and ...

The Scrum Master should do this because it is the most effective way to ensure that the Scrum Teams are self-organizing, cross-functional, and collaborative. The Scrum Master can help the Scrum Teams to understand the benefits of working together as one integrated team, rather than as separate component teams. The Scrum Master can also facilitate the communication and coordination among the Scrum Teams, and support them in resolving any dependencies or conflicts that may arise.