The document discusses population pyramids and groups countries into categories based on similar pyramid structures. It includes a key of 16 countries with their population pyramid diagrams. Countries are grouped into 6 categories based on similarities in their population distributions: Group A includes Afghanistan, Mozambique and Uganda; Group B includes Bangladesh and Haiti; Group C includes India and the USA; Group D includes Brazil, China, and Iran; Group E includes South Korea, Taiwan and Thailand; Group F includes Germany, Italy and Japan. Teachers are instructed to have students sort the countries into groups based on similar pyramid characteristics and make guesses about which countries are represented.