Which of the following is a main reason why vast parts of the african continent are virtually uninhabitable

Because it is to hot and there is basically no water for miles. Even you find water,  you would still need to purify it by boiling it. Hope this helps :)

isolationism is a doctrine practiced by the united states for much of its history with the aim of not intervening in external affairs that did not pose a real threat to their country. the united states managed to maintain a state of political isolation throughout the nineteenth century and the first part of the xx. few nations have been able to maintain such a position for such a long period of time. historians argue that it is largely due to geographical reasons, given the physical distance between europe and the usa. uu the venataja of this situation is that the national state can spend its resources in satisfying all the needs of its inhabitants, without the need to invest in armament and equipment for a war that does not directly affect the country.

internationalism is a political and cultural movement that advocates for greater political and economic cooperation among nations for mutual benefit. this novimiento was transformed over time, today it includes military intervention in international conflicts with the objective of maintaining peace. the advantage of this move is in the international contacts and the influence developed by the country that carries it forward.

between the two modes of relations between states, i prefer the first, since i believe it is of the utmost importance to satisfy the needs of citizens and work for their development and as a last option to act on the international level.

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).