Which of these states the significance of the timeline?

mark antony's defeat was the most important event in the history of the roman republic and led to octavian's alliance with egypt.
power struggles between men like julius caesar and ruling bodies led to the gradual transition from the roman republic to the roman empire.
roman dictators were often overthrown only after long periods in office, but octavian refused to follow this pattern.
the assassination of julius caesar led to a period of democracy and stability in the roman republic.