Why is an index contour different from other contour lines?   a. it indicates a greater change in elevation.   b. it is drawn more darkly on a topographic map.   c. it signifies where elevation begins to decrease.   d. it shows the elevation from which other points are measured.

d. it adversely affected american productivity

well this is going to be a long answer lol ok so the visigoths were a branch of the goths who frequently raided rome, uh the hunas attacked the guptas a lot and weakened them, uuhm of course the romans used math and science in there every day lives i mean they had a whole empire to run, and rome was split into east and west by a general named diocletian. hope this you! : )