Answer:
D
Explanation:
US troops were ill-prepared to fight in Vietnam’s environment.
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.
There are three main reasons for European Exploration. Them being for the sake of their economy, religion and glory. They wanted to improve their economy for instance by acquiring more spices, gold, and better and faster trading routes. Also, they really believed in the need to spread their religion, Christianity
Farming, making a living, slavery, religion, i don't know if this is exactly what you're looking for but heres a rough idea.