An analyst gathers the price-earnings ratios (P/E) for the firms in the S&P 500 and then ranks the firms from highest to lowest P/E. She then assigns the number 1 to the group with the lowest P/E ratios, the number 2 to the group with the second lowest P/E ratios, and so on. The measurement scale used by the analyst is best described as:（）

A. ordinal.

B. interval.

C. nominal.

落料是将（）与（）以封闭的轮廓线分开，而封闭线以内是（）。