Why are modern bridges longer and stronger than the other ones?

This chart shows american troop strength during what conflict? a) gulf war b) korean war c) vietnam war d) world war ii

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.

How did the grooms national product (gnp) of the united states change between 1940 and 1944