单选题 Which of the following is least likely to describe a cross-sectional data set?
A. An index's quarterly returns in 2011.
B. The annual sales growth of companies in mining industry in 2011.
C. Price-to-earnings ratios of publicly traded companies at the end of 2011.

【正确答案】 A

【答案解析】[解析] 选项A中的2011年每季度的回报是时间序列数据(time-series dada)。而另外两个选项，即2011年采掘行业的年销售增长率和2011年末的市盈率是截面序列数据(crosssectional data)。