In the United States, the Constitution is the ultimate "law of the land," meaning that the federal government has sovereignty over the states--although some powers are "shared".
<span>The word for an array of nonaligned or friendly states that cushion or protect a larger country from invasion, as happened with the former soviet union and its eastern european neighbors is the buffer zone. It is created to specific areas that needs to be protected such as restrictions on the use of resources of that area and the country do its best to create measures to improve the conservation value of that area.</span>
The fourth one is correct
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.
