Changes in the earth's climate caused ice sheets to grow and cover most of Canada and some of the northern US almost 15 000 years ago. This is known as the last Ice Age. For the last two million years, the earth has shifted between ice ages and warmer periods. Ice ages are caused by slight changes in the way the earth orbits around the sun. Huge continental glaciers or sheets of ice moved down from the Artic and covered Canada, North America and much of Europe.
Dewey Decimal and Library of Congress refer to library classification systems. The Dewey Decimal system is a library classification system created in 1876. The Library of Congress is a research library that is officially for the United States Congress, but is the de facto national library of the United States.
The answer is D. Create a system of retirement and unemployment insurance.
The government selected an age which they believed most people were retired by and the Social Service Administration allows people above that age to continue earning and income.
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