(A) The death of Tsar of Russia
(B) Germany invaded Poland
(C) The bombing of Pearl Harbor
(D) ** The assassination of Archuduke Fenard
EXPLANATIONS BELOW
Concept note-1: -The assassination of Austrian Archduke Franz Ferdinand (June 28, 1914) was the main catalyst for the start of the Great War (World War I).
Concept note-2: -When it was learned that the heir-apparent to the Austrian throne, Franz Ferdinand, was scheduled to visit Sarajevo in June of 1914, the Black Hand decided to assassinate him because of his perceived threat to Serbian independence.
Concept note-3: -The assassination of Archduke Franz Ferdinand was the immediate cause of a war between two great powers-Russia and the Habsburg Austro-Hungarian Empire.
Concept note-4: -The assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, and his wife Sophie in Sarajevo (the capital of the Austro-Hungarian province of Bosnia-Herzegovina) on 28 June 1914 eventually led to the outbreak of the First World War.