Building through the Sierra Nevada Mountains was very difficult and dangerous. Temperatures were freezing during the winter and in one year alone there were 44 storms.There was the great danger of an avalanche for the men working through 18 feet of snow and camping on the tunnels beneath it. Creating tunnels through the mountains required blasting with nitroglycerin. Advancing at one foot of mountain at a time, a total of 11 tunnels was created.
A war instigated by a major power that does not itself become involved. for example the cold war and their proxy wars which are Vietnam war, korean war, ect.
I'm pretty sure the answer is D. poor working conditions, because people back then were very serious when it came to working, since they needed the money badly. All of the other answer choices are factors that led to the Great Depression.
