Which additional natural resource would be most important to a society wanting to become industrialized

Contour lines are described as the places having equal elevation and they never intersect one another.

The index contours are the contour lines that are usually highlighted by a thicker contours, dark in color and they are shown as every fifth contours. The height of these contours are mentioned in numbers adjacent to these lines. The presence of index contours makes it easy to understand the topography of an area.