C. Relationship among current financial balances and prior balances, forecasts, and non-financial data

Explanation:
Analytical procedures involve evaluating relationships among financial and non-financial data to identify inconsistencies, trends, or unexpected variances. Option C correctly describes an analytical procedure used to produce audit evidence by examining relationships among current financial balances, prior balances, forecasts, and relevant non-financial data. The other options involve direct evidence-gathering methods, such as confirmations, physical observation, and document examination, rather than analytical procedures.