In order to win an election a major party must revive votes
The most powerful was economic prosperity of European countries. They could exploit the land and the people of Africa and take their raw resources such as diamonds for example and take them to Europe. There they would be able to make goods with them and sell them to people for a lot of money and this meant that they would grow vastly richer than they were before.
The correct answer among all the other choices is A. the revival of democratic revolutions, and nationalism. This is a factor that caused German and Italian unification. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.