Susie Le is performing an audit on the Purchases and Payables cycle for Bearspaw Credit Union Ltd. and discovers a substantial payable that was recorded without an invoice attached to support the amount of the liability. She sends an email to the Controller, who provides her with an Excel spreadsheet prepared by the Controller that supports the amount recorded. Susie thanks the Controller but insists on receiving a copy of the supplier invoice. Susie's actions are an example of _______.

A. professional skepticism

B. audit data analytics

C. insubordination

D. test of internal controls