Question

how is elevation shown on a topographic map?
intermediate contours
index contours
contour intervals
contour lines

Explanation:

Index contours, intermediate contours, and contour intervals are all components related to representing elevation, but the overarching feature that directly shows elevation on a topographic map is contour lines. Index contours are labeled contour lines, intermediate contours fill in between them, and contour intervals are the elevation difference between lines—all rely on contour lines as the base method.

Answer:

contour lines