Final answer:
Colonialism and world system theory explain the stratification of the world's nations by highlighting how the extraction of wealth by European merchants and governments and the exploitation by core nations contribute to global inequality.
Step-by-step explanation:
Colonialism and world system theory offer explanations for how the world's nations became stratified. Colonialism refers to the global system through which European merchants and governments extracted wealth from other parts of the world, resulting in inequality between former colonizers and colonies. World system theory, proposed by Immanuel Wallerstein, categorizes countries into core, periphery, and semi-periphery based on their economic status and level of exploitation. This theory highlights how core nations exploit peripheral and semi-peripheral nations, contributing to global stratification and inequality.