Answer:
<em>After 133 B.C.E..the republican form of government broke down and resulted in a series of civil wars which ended with </em><em><u>Octavian</u></em><em> defeating </em><em><u>Mark Anthony </u></em><em>and </em><em><u>Cleopatra. </u></em>
I am unsure of the options but it was Octavian's victory over Mark Anthony and Cleopatra in Egypt that ended the Roman Republic Civil wars.
From 133 B.C.E, the Roman Republic saw various civil wars as men like Sulla, Julius Caesar and Octavian vied for control of the Republic over various generations.
Sulla was made dictator after his civil wars and so was Julius Caesar after he defeated Pompey. Caesar was then killed by Brutus and other senators who fled as Ocatavian and Mark Anthony hunted them and their armies down to avenge Caesar.
Mark Anthony and Octavian fell out afterwards and another civil war began that ended with Octavian defeating Mark Anthony and Cleopatra and taking over Egypt as his personal property.
This marked the end of the Roman Republic as Octavian became Augustus, the first emperor of Rome.