Which of the following factors led to the development of ancient civilizations

It’s a complex process. First an area’s population gets too large to live by hunting and gathering. So people start living where the hunting is best (eg, following a particular herd) or settling down where the gathering is best, or combining the two (farming).

When that leads to another unmanageable increase in population we get villages, then towns, then cities, in a continuous attempt to intensify production and feed more people. Voila! Civilisation!

Sometimes a civilisation will arise in response to an aggressive civilisation next door, that wants to take territory. The characteristics of the secondary civilisation will be a bit different from a primary civilisation at first but after that, development will follow a standard pattern until it collapses.

four sitting presidents have been assassinated while in office but the first was abraham lincoln,