(A) He owned a lot of businesses.
(B) He was their leader.
(C) ** He would be the next leader.
(D) He was the richest man in Austria-Hungary.
EXPLANATIONS BELOW
Concept note-1: -The assassination set off a rapid chain of events, as Austria-Hungary immediately blamed the Serbian government for the attack. As large and powerful Russia supported Serbia, Austria asked for assurances that Germany would step in on its side against Russia and its allies, including France and possibly Great Britain.