Why was imperialism an important underlying cause of World War I?

Question 3 options:

a/The United States remained isolated when they took over Cuba, Guam, the Philippines, and Hawaii.


b//Colonies were adapting to new rules set forth by their governments and enjoyed the perks of being colonized.


c/European kings taxed their people to the point of exhaustion.


d/The great powers of Europe were competing for land around the world.