Why can't contour lines cross?
a. mountains and valleys are different.
b. a location can only have one elevation.
c. it would make the map too difficult to read.
d. terrain can only be going up or heading down.

a location can only have one elevation.

Explanation:Contour lines can never cross on a topographic map. This is because they represent the same elevation of the land surface. A particular point of a land cannot be at two or more than one elevation and this means that only one contour line can pass through that particular point.

All points present along a contour line represent just a single elevation. The most prominent features on a topographic map are the contour lines. The contour lines are the lines that connect points of the same elevation.

And each contour line represents a different elevation so you can't have two (2) different elevations on the same point.

There are 3 kinds of contour lines you can find on a map:

Intermediate

Index

Supplementary.

doctrine that the us had the right to expand throughout north america.