Petroleum has the following positive contributions to the Nigerian economy except

Petroleum has contributed significantly to the Nigerian economy in various ways. It is a major source of government revenue, and it has created job opportunities for many people in the country. Also, the development of the petroleum industry has led to the establishment of various infrastructure such as roads, bridges, and hospitals, which have benefited the nation. However, one negative impact of the petroleum industry in Nigeria is that it has led to the development of a mono economy. This means that the economy of Nigeria has become highly dependent on petroleum, which can be risky in the long run as the demand for petroleum may decline or the oil reserves may eventually run out. This over-reliance on oil exports can leave Nigeria's economy vulnerable to external shocks and fluctuations in oil prices, which can have a devastating impact on the country's economic stability. Therefore, all of the options listed except for "development of mono economy" are positive contributions of the petroleum industry to the Nigerian economy.