Write the next sentence in the following story.

How to read topographic maps
Use the thicker contour lines to determine the elevation.
Contour lines represent paths or segments of the earth. Topographic maps are covered in contour lines.

OPTIONS:
I. Some contour lines are thicker, known as indexed contour lines. They have a number next to them that shows you the elevation of that path or segment.
II. They serve to guide you in one direction. These lines are perhaps the most important lines to reference when transferring data from a geobody/mountain to a geoshell.
III. They can be used to indicate local areas by elevation, even if it is easy, incredibly dangerous, and challenging. As a result, topographic maps are the norm for landmasses in the western hemisphere.
IV. The darker the lines, the darker the topography/terrain. Choose a map with small sections of topography and large sections of landscape.. The answer should be
I.