This is true. The homestead act gave people huge properties for a small price if they were willing to work on the field for 5 years. After 5 years it would become their and they could do with it as they wished.
A wall stands using gravity. It is constantly being pulled down. Many also place them in ways that they dig into the ground, and almost make a socket just for the wall to be placed, using the land that is there. More and more walls are placed and eventually, they make flooring and a roof.
Hope that helped!
I'm not 100% positive but it is South Korea
I believe your answer would be A- Farmers and urban dwellers.
Hope this helps. Correct me if I'm wrong.