1. The simplest circular-flow model shows the interaction between households and firms. In this model: A. only barter transactions take place. B. households and firms interact in the market for goods and services, but firms are the only participants in the factor markets. C. firms supply goods and services to households, while households supply factors of production to firms. D. attention is focused on "real" flows of goods, services, and factors of production, but money flows between households and firms are ignored for simplicity. E. firms supply factors of production to households, which, in turn, supply goods and services to the firms