In a Simple Circular-Flow Diagram,total Income and Total Expenditure Are

In a simple circular-flow diagram,total income and total expenditure are

A) never equal because total income always exceeds total expenditure.
B) seldom equal because of the ongoing changes in an economy's unemployment rate.
C) equal only when one dollar is spent on goods for every dollar that is spent on services.
D) always equal because every transaction has a buyer and a seller.