The western third of the state reveals areas of forests and fertile lowlands, and the Olympic Peninsula surrounded by the ocean and Puget Sound. The middle third is dominated by the mountain terrain of the Cascade Range. The eastern third shows large areas of flat pasture that shows up light brown because of the drier climate. Use the map to answer the question.
How did ice ages affect the land that became western Washington?
A. Glaciers carved a large valley that later flooded and became Puget Sound.
B. Glaciers unclogged large rivers that later formed Lake Missoula.
C. Ice dams gave way to form scablands that support little life.
D. Coulees formed the Columbia Plateau.