The idea that individuals, companies, and countries should specialize in what they do best is most closely associated with

Comparative Advantage

Explanation: They theory of comparative Advantage can be described as an idea which involves individuals, organizations or countries to produce, manufacture, specialize or focus on goods or services that presents them a lower opportunity cost than other related or substitute goods and services.

The term opportunity cost could be described as the potential benefit one stands to lose by choosing a certain product over another.

Economically, one should choose a product or service that offers a lower opportunity cost ( that is, a lower potential loss than its substitute.)

the correct answer is c.