5.The expected rise in the price of oil could be a serious impact to industrialized nations and severely diminish the possibility to have an economy free of inflation. (A) be a serious impact to industrialized nations and severely diminish the possibility to have (B) seriously impact on industrialized nations and severely impede the possibility to have (C) seriously impact on industrialized nations and severely impede the possibility of having (D) have a serious impact on industrialized nations and severely impede the possibility to have (E) have a serious impact on industrialized nations and severely diminish the possibility of having
I looked up the meaning of "impact" in Dictionary.com, their comment seems to me that the usage of "impact on" as verb is not as widely accepted as noun by orthodox American grammar. I also found comment similiar to what "bluestone1" replied. So I think you'd better take that "impact on" is used as a noun