What was happening in muslim lands that led european christians to begin going on crusades at the end of the 11th century? for what reasons did europeans join the crusades?

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.