Europe. North America and Africa
It would be "d. eight-hour days" that was not a problem faced by workers in nineteenth century mills or mines, since legislation advocating for strict working hours did not come about until the Progressive Era.
The constitution of the United States set up a set of checks and balances among the three branches of government. The Legislative, Executive and Judicial powers constitute the structure of the american government, and they have power to check each other's way of work.
One example of the check and balance system is that the Supreme court of the United States may check congress by declaring a law passed by this one as unconstitutional. This is a clear check limit used against the legislative power, that is the congress. But on the other hand, the power is balanced because the members of the Supreme Court are appointed by the President of the country (the Executive power), and to be appointed they have to be approved by the Congress.
Nigeria had much division between tribal/ethnic groups vying with one another for power, and thus were not working together for a united purpose. Nigeria's wealth of natural resources also gave them much to be fighting over as the groups each sought advantage.
Botswana, on the other hand, was one of the poorest countries in the world when it gained its independence from Britain in 1966, and it avoided infighting and political corruption like that seen in Nigeria. They have been a multi-party democracy since that time -- the longest-running multi-party democracy on the African continent. Botswana enjoyed significant economic growth also as it worked together politically.
