What are risk and assumptions in M&E?

What are risk and assumptions in M&E.
In Monitoring & Evaluation, assumptions and risk forms part of any M&E plan. Risk and assumptions are important for making sure that the design of our results chain is credible.
Assumptions are the preconditions necessary for projects or programs to achieve results. So our assumptions and preconditions needs to be reasonable, if results are to be observed as expect.
Risks are factors that could significantly affect the achievement of the project or program results and targets.
So when identifying the risk for projects and programs we must think what can go wrong:
Questions like
• What could shift in the external environment?
• What are the external forces acting against project success?
• Whats other factors like resources, implementation capacity etc. can hamper the project.