Buying and Selling is:
O Economy
O Socialism
O Trade
O Capitalism

I'd say Capitalism

Explanation:

It is part of economy as a whole, but it is also capitalism.

Definition of economy: the wealth and resources of a country or region, especially in terms of the production and consumption of goods and services.

Definition of capitalism: an economic and political system in which a country's trade and industry are controlled by private owners for profit, rather than by the state.

louverture's prominent role in the haitian success over colonialism and slavery had earned him the admiration of friends and detractors alike.

explanation:

toussaint louverture began his military career as a leader of the 1791 slave rebellion in saint-domingue; he was by then a free man and a jacobin.

demand is the need and oportunity to buy a given good or service.