OG-33－purchasing power

33. Rural households have more purchasing power than do urban or suburban households at the same income level, since some of the income urban and suburban households use for food and shelter can be used by rural households for other needs.
Which of the following inferences is best supported by the statement made above?
A. The average rural household includes more people than does the average urban or suburban household.
B. Rural households have lower food and housing costs than do either urban or suburban households.
C. Suburban households generally have more purchasing power than do either rural or urban households.
D. The median income of urban and suburban households is generally higher than that of rural households.
E. All three types of households spend more of their income on food and housing than on all other purchases combined.
选项用排除法后剩下正确答案B，可本题中的purchasing power（经济学意义上的购买力一般用于比较不同国家货币的购买能力，放在此处说不通啊）该怎么理解呢？

b，没错

因为在这道题里是比较城市居民和乡村居民的收入分配状况，在同等收入水平下，乡村居民在食物和房子上的花费更少

所以相应也就有更多的富余资金来支付其他的费用

所以答案是B

请问花在房子和食物上的钱不算作购买力的一部分吗？