Keith Keeley, an associate at Friedman, Harris, and Levinsky LLC, was requested by a Managing Director of the firm to help construct the consumer price index (CPI). Keeley sought to determine which goods and services to include in the index by observing what a typical U. S. household purchases. He then took a large survey of individuals to determine what percentage of their disposable income they spend on each of the items and used these percentages as the weights for the major categories in the CPI. The steps that Keeley undertook are all part of which stage in constructing the CPI index（）

A. Select the CPI basket.

B. Calculate the CPI.

C. Conduct the monthly price survey.