When faced with a change, it is necessary for a project manager to thoroughly assess the potential impact of that change on the project's timeline, budget, and resources. Therefore, the first best step is, indeed, to 'Assess the potential impact of these changes on the project's timeline, budget, and resources, then prepare a change request for stakeholder approval.' This approach ensures that all potential issues that the change might introduce are identified and that the stakeholders are given an opportunity to understand and approve the change. The other three options are wrong because: - 'Immediately rush and implement the changes without careful planning': This action is reckless and can potentially introduce more risks and issues into the project, endangering its success. - 'Insist on sticking to the original plan and ignore the change': This response is unprofessional and ignores the importance and value of the new environmentally friendly energy sources which could have long-term benefits to the company beyond this specific project. - 'Resign from the project due to the introduced complexity': This action is not only unprofessional but also counterproductive. Challenges will always arise in projects and it is the project manager's role to navigate through these challenges and find solutions, not to abandon the project.