How does the gradient of a river result in the river changing course ?

Width and depth increases as more water is added from tributaries. Gradient (the slope of the land) decreases as rivers flow because the river meanders across the land rather than erode into it and follow a straight path as it does in the source.

the precambrian aged rocks could be found in australia. australia is a region that has a lot of ancient civilization history from million years ago. in this region, there are a lot of recognizable fossils buried in its land which is considered a precambrian-aged rocks

answer(c) carved on a babylonian clay tablet that showed earth as a flat circular disk;