What major event happened that was considered the real beginning of ancient egypt?

The dynastic period started with the reign of Egypt's first king, Narmer, in approximately 3100 BCE, and ended with the death of Cleopatra VII in 30 BCE. During this long period there were times of strong centalised rule, and periods of much weaker, divided rule, but basically Egypt remained one, independent land.

Ithink the answer should be a.