On a topographic map, what is used to show elevation?

Contour Lines:Contour lines are used to determine elevations and are lines on a map that are produced from connecting points of equal elevation 

Assuming that this is referring to the same list of options that was posted before with this question, the correct response would be the one having to do with the fact that World War II greatly increased domestic production, which greatly increased the salaries and social standing of many working Americans.