Pls help me need it bad

Which factor has played the most important role in changing the way history is studied over time?

7. how did the early egyptians use the flooding of the nile river to their advantage? they diverted the water to flood their enemy's lands and destroy their crops. they created an easier way to travel to the mediterranean sea and the indian ocean. they established a new water-based athletic event for the ancient olympics in greece. they devised an innovative irrigation system, which created a surplus of food.

How did agitators on both sides of the slavery issue make things worse? by putting out bounties on certain peopleby committing murderthrough their writingsby compromising on too many things