Uncontrollable risk

Which of the following risks may be an uncontrollable risk?
Excessive change orders
Workmanship errors
Material costs
Scope growth

Can somebody let me know why the answer is C.
My guess was D

admin's picture

Material cost is driven by market and not directly within the control of project manager or project management team. Its and external factor and hence cannot be controlled by PM.

Thanks admin. I was just thinking the sponser can increase budget, increase scope and can extend the project time line as well, for which the PM just cannot deny.