The project D. Building the Transcontinental I believe is the one that led to the creation of a system of time zones across America
The destruction that resulted from war or siege including the purposeful burning of an enemy city’s fields.
I believe both originated and evolved in the United States during the late 1940s and early 1950s
The eastern and western deserts prevented invaders from the east and west. The deserts were a hard climate to travel through. Therefore, nobody could walk across to conquer Egypt. Furthermore, the cataracts in the Nile to the south protected the Egyptians from lands below them. So the answer would be that The Nile protected the Egyptians from invasion.
