Concept:Petroleum brings many benefits to Nigeria, but a mono-economy is a negative outcome, not a positive contribution.
Explanation:Petroleum generates employment for Nigerian citizens.
It serves as a major source of government revenue.
It supports infrastructure development, such as roads and power projects.
However, excessive reliance on oil creates a mono-economy.
A mono-economy limits economic diversification and is generally considered a disadvantage.
Therefore, the option that is not a positive contribution is the development of a mono-economy.
Answer:C. Development of mono economy.