As the polar ice caps melted and the sea level rose more than 300 feet above present day levels. a sharp drop-off that was left behind by this ancient shoreline can now be seen. this sharp drop-off called a typically visible when crossed by a river because often there will be rapids or waterfalls. a) fall line b) sand hills c) coastal plain d) barrier islands

Option A) Fall Line

Explanation:

A fall line is a geological boundary that is formed between an upland region and a plain beneath. Usually, the regions are identified by falls or rapids when rivers and streams cross or meet.

One interesting feature is that the fall lines are formed when rivers meander through regions of weak rock structure. Normally, the rock structure is sedimentary rock structure (layered). The rivers tear into the earth by erosion, abrasion and attrition.

In addition, plate tectonics play an important role. The movement of the earth's plates causes the falls. Some are formed by the rapid freeze-thawing action of large blocks of ice.

what type of charge does it have? negative