Question

which statement describes one characteristic of index contour lines?
they appear thinner and lighter than other lines on a map.
they show regions where a difference in elevation exists.
they show the locations of roads and paths on the landscape.
they show ratios used to determine the actual distance on a map.

Explanation:

Index contour lines are darker and thicker (not thinner and lighter) than other contour lines. They are used to show elevation differences. Road/path locations are shown by specific map symbols (not index contours). Ratios for actual distance are scale bars or representative fractions (not index contours). So the correct characteristic is that they show regions where a difference in elevation exists.

Answer:

They show regions where a difference in elevation exists.