What are three ways historians used to study prehistory

This was an order issued during the civil war by president lincoln ending slavery in the confederate states

What happened as agriculture became entrenched in the south ?

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.