Colors on a physical map might never used to show an areas , or height above sea level

Green is often used for forest, tan for deserts, and blue for water. A map usually has a legend, or key, that gives the scale of the map and explains what the various symbols represent. Some maps show relief, or changes in elevation. A common way to show relief is contour lines, also called topographic lines.

high entry costs prevent new producers from entering the market.

explanation:

an oligopoly is a term used to clarify the structure of a particular market, industry, or organization. a market is considered oligopolistic or amazingly focused when it is shared between a few companies.