What is a treaty?
a- an informal agreement between two or more nations
b- a formal agreement between two heads of state
c- an informal agreement between two heads of state
d- a formal agreement between two or more nations

Following archduke franz ferdinand's assassination, austro-hungarian leaders: a. aided the ottoman empire in its campaign to keep serbia under its control. b. executed nearly all prominent serbs living in austria-hungary c. threatened to invade serbia if serb leaders did not agree to a set of strict demands. d.. formed an alliance with great britain to protect austria-hungary from future attacks.