The circular-flow diagram is an example of ______.
A、a laboratory experiment
B、an economic model
C、a mathematical model
D、All of the above are correct.
The circular-flow diagram is an example of ______. A、a labo - 3. Circular-Flow Diagram and PPF - 微观经济学(全英) - 重庆高校在线开放课程平台 | 大学网课搜题引擎