I believe the correct answer is B. The alliance between Serbia and Austria-Hungary sparked unrest that stemmed from the failure of the Treaty of Paris.
The correct answer is C) Alliances forced many countries to go to war in support of either Austria-Hungary or Serbia.
The assassination of Archduke Franz Ferdinand by a Serb lead to World War I in that "Alliances forced many countries to go to war in support of either Austria-Hungary or Serbia."
On June 28, 1914, Archduke Franz Ferdinand and his wife Sophie were assassinated in Sarajevo. The Archduke had planned a trip to Sarajevo to oversee the Austrian-Hungary troops established in that region. The assassination increased tension in central Europe and the incident was one of the reasons that started World War 1.
