Answer: Options A, B and D.
Explanation: shields are layers of old rocks that metamorphosed as a result of mountain-building events. Shields also have sedimentary layers that usually rest on the lava of the rock.
Westward expansion meant that the US acquired ever increasing amounts of land, and needed people, farmers, to settle there so it could maintained without a huge military presence
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Answer:</h2>
Demography is the study of human population.
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Explanation:</h2>
Demography studies most if not all aspects about human population. It checks births, death, sex, migration, etc. and in turn, when we describe the population, it is normally from pertaining to demographic. Demography is also involved in other disciplines such as sociology, economics, statistics, etc.
Through demographics, the necessary departments get to understand people and their needs better. Countries economic decisions is one example that depends on demographic studies. It also affects other areas such as the planning, labor markets analysis, and etc.
