Two features uses demerits for
relief map

Relief Map : Features

Relief Map : FeaturesA relief map will show the elevation, meaning the high points, and the depressions, meaning the low points, of a given area. For example, if you live next to mountains, you'll see a lot of elevation markings since they're so tall and we know their exact height.

i'm sure the answer you are looking for would be

a. an ice age

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