Why did European countries establish colonies in Africa during the 19th century? a they were rivals during the cold war

b they wish to expand their economies

c the American revolution made it possible

D the Africans kingdoms asked for Europe help

I'm pretty sure the answer is b.)

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).