How did the separate of kingdoms of egypt unite? ?

At this time the capitol of Upper Egypt was known a Nekhen while the capitol of Lower Egypt was Nekheb later called Heiroconopolis (the falcon city). 
After many years of warfare it was the warrior-king Menes (c3000BCE) whose armies finally defeated the armies of the southern nomes or city states, that are collectively known to us as Upper Egypt. 
hope this helps

D

Explanation:

Lets use the process of elimination. A we can cross out because people have questioned whether or not america just wanted to gain power over Europe. B we can cross out because there was foreign debts. C we can cross out because their has been people who have considered if America just wanted to dominate Europe. So D is the answer.