One important word appears in all three documents, what is it?

Brainliesttt !me : ) describe the conflict and changes in israel:

How did inca develop their road system? a) they used mortar to hold the stones together.b) they built suspension bridges over rivers. c) they mixed copper and stone together to make the blocks.d) they laid roads in the cities, not in the less densely populated deserts.

World war 2 was caused, in part, by which of these factors?