What issues increased American prejudice toward immigrants in the mid - 1800s ? No link please

Aside from low birthrates and high death rates, what can cause a country’s population to decline

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.

The answer because i don’t know it someone