Final answer:
The auditor is testing the 'rights and obligations' (2) assertion when reviewing bank confirmations for liens on receivables to ascertain the company's legal claim to those assets and any associated encumbrances.
Step-by-step explanation:
When an auditor is reviewing bank confirmations for any liens on receivables, they are testing the rights and obligations (2) assertion. This assertion pertains to the company's legal rights to the receivables and whether there are any obligations such as liens or other encumbrances on those receivables. Thus, confirming with the bank whether there are any liens helps auditors determine the extent to which the receivables represent realizable resources that the company has the right to use without restrictions.