Choice "A" is correct. The examination of client records documenting the use of EDP programs is a test of controls.
Choice "c" is incorrect. Confirmations of receivables verifying account balances is a substantive test, not a test of controls.
Choice "d" is incorrect. Obtaining letters of representation corroborating inventory pricing is a substantive test, not a test of controls.
Choice "b" is incorrect. Attorneys' responses to the auditor's inquiries are part of a substantive test, not a test of controls.
