How did nationalism, alliances, imperialism, and military build-ups contribute to the start of world war i? what alternative solutions could have been used to prevent the war beginning (based on historical evidence)?

Alliances- Countries felt loyal to one another so if one was in trouble then the others would come and help out.
Nationalism- To prove that their country is the best.
Imperialism- many European countries sought more expansion
Military- Strong military force.

WWl could have been prevented since the German support from Austria-Hungary.  The "triple alliance" of Germany, the Austro-Hungarian Empire, and Italy was predicated on mutual defense, not on mutual aggression - this is what allowed Italy to abstain from the early phases of the war and eventually to join the Entente Powers.