1. The problem asks for the most effective graph type to display proportions of different types of waste in a landfill. 2. A pie chart is ideal for showing proportions or percentages of a whole because it divides a circle into slices that represent parts of the total. 3. Other options like bar graphs show quantities but do not emphasize proportions as clearly. 4. Histograms display frequency distributions for continuous data, and line graphs show trends over time; both are less suitable here. 5. Therefore, the most effective graph to display proportions of different waste types is a pie chart.