The correct answer is - Competition to develop strong economies and build large empires.
There were lots of tensions in Europe about the shares that each colonial country had on the other continents were the natural resources were abundant. While some considered that they had won this territories fair and square, others were on the opinion that they should get some of the colonies under their control. The background of this was of course the economy, and the competition between the nations to be wealthier, military stronger, and enlarge their territories. Unfortunately, these tensions led to a World War.