Answer:
The first one would be that Serbia totally accepted the Austro-Hungarian ultimatum to them after the assassination and the other would be if Russia and other great powers didn't support Serbia in the dispute.
Step-by-step explanation:
Ferdinand was killed on June 28th 1914 by a Serb called Gavrilo Princip. Austria-Hungary blamed Serbia and asked Serbian authorities to allow them to research what happened on the soil of Serbia. The ultimatum sent to Serbia was unacceptable for the Serbian government and that is why they refused to accept one of ten terms. After Austria-Hungary declared war on Serbia, Russia and other forces started to enter the war.