[单项选择]

A scientist who does research in economic psychology and who wants to predict the way in which consumers will spend their money must study consumer behavior. He must obtain data both on the resources of consumers and on the motives that tend to encourage or discourage money spending.
If an economist were asked which of three groups borrow most -- people with rising incomes, stable incomes, or declining incomes -- he would probably answer: those with declining incomes. Actually, in the years 1947 -- 1950, the answer was: people with rising incomes. people with declining incomes were next and people with stable incomes borrowed the least. This shows us that traditional assumptions about earning and spending are not always reliable. Another traditional assumption is that if people who have money expect prices to go up, they will hasten to buy. If they expect prices to go down, they will postpone buying. But research surveys have shown that this is not always true. The expect
A. rely on traditional assumptions about earning and spending
B. try to encourage or discourage consumers to spend money
C. carry out investigations on consumer behavior and obtain data on consumers’ incomes and money spending motives
D. do researches in consumer psychology in a laboratory