(A) ** A system of secret alliances among European powers
(B) Mutual distrust of the United States
(C) Everyone wanted to split the Austro-Hungarian Empire
(D) War would stimulate their struggling economies.
EXPLANATIONS BELOW
Concept note-1: -The assassination of Franz Ferdinand stoked old tensions beyond the Balkans. The crisis spread as other powers pledged support for either Austria or Serbia. Austria knew that conflict with Serbia would likely involve Russia, which saw itself as Serbia’s protector. Austria-Hungary turned to its own ally.
Concept note-2: -The immediate reason for Austria’s ultimatum was the assassination of Archduke Franz Ferdinand and his wife Sophie in Sarajevo, Bosnia on June 28, 1914 by the Bosnian Serb nationalist, Gavrilo Princip.
Concept note-3: -Explanation: The assignation of a crown prince of the Austrian Hungarian empire cause the Austrian Hungrian empire to declare war on the small Slavic country of Serbia. Slavic Russian who had an alliance with Serbia then declared war on the Austrian Hungrian Empire and mobilized its troops to defend its ethnic ally.
Concept note-4: -A defensive Dual Alliance system between Austria-Hungary and Germany was formed to counter the potential Russian Aggression. Later in 1882, Italy joined the agreement which came to be known as the triple alliance.