(A) Militarism
(B) Alliances
(C) Imperialism
(D) ** Nationalism
EXPLANATIONS BELOW
Concept note-1: -Austria had long seen Serbia as a threat to the stability of its multi-ethnic empire. Austria’s annexation of Bosnia in 1908 and Serbian ambitions to unify south-east Europe’s Slavic people further strained relations in this volatile part of Europe.
Concept note-2: -The threat of Serbian nationalism This was because Serbia was growing in power and becoming a magnet for the South Slav people, including Slovenes, Croats, and Serbs, most of whom lived within Austria-Hungary. Conrad von Hötzendorf had called for war with Serbia a dozen times before 1914.
Concept note-3: -Answer and Explanation: Nationalism led to the breakup of the Austro-Hungarian Empire because it fostered a sense of identity and allegiance among different ethnic groups within the empire. Each group began to see itself as separate and distinct from the others, leading to secession and independence calls.