The most significant factor that contributed to international instability following the Versailles Treaty is primarily B) economic factors.
The Versailles Treaty imposed heavy reparations on Germany, which caused severe economic hardship and contributed to hyperinflation in the early 1920s. This economic distress created widespread discontent among the German populace, undermining trust in the Weimar Republic and contributing to the rise of extremist political movements, including the Nazis, who capitalized on the grievances stemming from the Treaty. The economic instability not only affected Germany but also had broader consequences for Europe, as it disrupted trade and exacerbated the global economic conditions leading up to the Great Depression.
While diplomatic, military, and informational factors also played roles in international instability during this period, the economic repercussions of the Versailles Treaty were critical in fostering the conditions that ultimately led to the outbreak of World War II. Thus, economic factors are the most salient in critiquing the Versailles Treaty in the context of international instability.