Final answer:
The correct answer is c. Bias in the items the auditors decide to select for testing.
Step-by-step explanation:
The correct answer is c. Bias in the items the auditors decide to select for testing. In accordance with the independence standards of the GAO (Government Accountability Office), auditors must not have any bias in the items they select for testing. This means that they should not favor or prioritize certain items based on personal opinions or preferences. The other options listed are examples of external impairment of independence because they involve external pressure or influence that could compromise the auditor's ability to perform an unbiased audit.