What are the three types of contour lines on a map?

The three types of contour lines on a map are index, intermediate, and supplementary lines. Index lines are typically the thicker and darker contour lines that are labeled with elevation values, providing a reference for understanding the terrain's elevation. Intermediate lines, which are thinner than index lines, are used to represent the terrain's elevation at intervals between the index lines. Supplementary lines, which are even thinner and often dashed or lighter in color, indicate subtle changes in elevation and are used for more detailed representations of the terrain.

This classification is essential for interpreting topographic maps, as it helps in visualizing the landscape, understanding steepness, and planning routes. The other options do not accurately reflect the standard terminology used in map reading and understanding contour lines. Understanding these three types helps soldiers and outdoor enthusiasts navigate and analyze geographical features effectively.