To what extent was the Treaty of Versailles responsible for the outbreak of World War 1?
The previous post is quite accurate. I would only add that one of the realities revealed by the Treaty of Versailles is that those who win a war can actually be guilty of poor judgment in drafting the treaty that ends the war. Though American President Wilson sought a more approachable understanding of peace, he was outvoted by his French and British counterparts who sought to punish and make an example out of Germany. This invariably gave forces in Germany, such as Hitler, the ammunition needed in order to rally public support in one of the most intense examples of "us versus them." The treaty ended up concluding World War I and helped to cause the outbreak of World War II.
In case you are referring to what parts of the Treaty are related to the causes of World War I. The answer to that would be many of them.
Wilson's Fourteen Points, which were his framework for world peace after World War I, included obvious causes of war such as battles for control of the oceans and waterways, alliances in World War I which gave countries a sense of overconfidence in victory, and more likely to start wars, and national self-determination - minority populations living within imperial borders. He sought to address all of these, and create a League of Nations in the Treaty of Versailles.
The Treaty of Versailles had nothing to do with the outbreak of World War I. The Treaty of Versailles was the treaty that was made after the war ended and so it could not possibly have had anything to do with causing that war.
You can definitely say it helped to cause World War II, though. It made Germany feel very angry and it made Germans feel that they had been treated unfairly. Because of this, Germans felt they had a score to settle and that helped cause them to support Hitler as he tried to get revenge for the Treaty of Versailles.