问题
单项选择题
An analyst does research about the classification of products. If income increases from $36 000 to $40000, and the quantity demanded for a product increase from 101 to 121, the product is best described as a(n):（）
A. necessity goods.
B. normal goods.
C. inferior goods.
答案
参考答案：B
解析：
收入增加，对这种商品的需求增加，表明该种商品的收入弹性大于0，其属于正常商品。劣等品的收入弹性小于0。弹性=[(121-101)/111]/[(40000-36000)/38000]=0.1802/0.1053=1.7113。弹性小于1，说明是必需品；弹性大于1，说明是奢侈品。