An auditor noted that client sales increased 10% for the year. At the same time, COGS as a percentage had decreased from 45% to 40%, and year-end accounts receivable had increased by 8%. Based on this information, the auditor interviewed the sales manager, who stated that the increase in sales without a corresponding increase in COGS was due to a price increase enacted by the company during the year. How would the auditor test the sales manager's representation?

A. Reviewing customer contracts.

B. Confirming sales transactions with customers.

C. Analyzing pricing policies and historical data.

D. Inspecting shipping and billing documents.