At which point of the project is the uncertainty the highest and the risk of...

According to the PMBOK® Guide, specifically in the sections covering Project Stakeholders and Governance and Project Life Cycle, there is a clear relationship between the project timeline and the levels of uncertainty and risk.

Risk and Uncertainty: These are at their highest at the start of the project. This is because at the beginning, the least amount is known about the project ' s requirements, stakeholders, environment, and technical challenges. As the project progresses, more information is discovered, and more work is completed, which progressively reduces uncertainty.

Probability of Failure: The probability of failing to complete the project is greatest at the start. As the project moves toward completion, the probability of success generally increases because the remaining work and the number of unknown variables decrease.

Cost of Changes vs. Risk: It is important to distinguish this from the cost of changes. While risk and uncertainty are highest at the start, the cost of making changes is lowest at the start and increases significantly as the project nears completion.

Analysis of other choices:

Choice A (Final phase of the project) and Choice C (End of the project): At these points, uncertainty is at its lowest because most of the work has been completed and the outcomes are known. While the impact of a risk occurring might be high (costly), the overall level of uncertainty is minimal.

Choice D (Midpoint of the project): By the midpoint, many initial risks have been mitigated or have passed, and the project team has a much clearer understanding of the path to completion than they did at the initiation.