You can enable expense auditors to audit expense reports for specific business units by assigning them specific expense auditor data roles for the business units. For example,to allow an expense auditor to audit expense reports for the Vision Operations and Vision Services business units, assign the Expense Auditor Vision Operations and Expense Auditor Vision Services data roles, respectively, to the expense auditor.
References:https://docs.oracle.com/cloud/farel8/financialscs_gs/FAWDE/F1005004AN1204B.htm

D: (not C): You can enter a credit memo against a fully billed purchase order (use negative quantity amounts to enter a credit memo), as well as invoice against multiple purchase orders. However, the currency and organization of all items on an invoice must be the same. The organization is the entity within the buyer'scompany that you are invoicing.
IncorrectAnswers:
E: After you submit an invoice, you cannot change the invoice.
References:https://docs.oracle.com/cd/E18727_01/doc.121/e13414/T463223T463232.htm

New expense report containing disallowed expense items is immediately created.
Expense report isn't eligible for expense reimbursement.

When you submit a "payment process request", you can enable the Apply credits up to zero amount payment option. Enablingthe option causes the payment process to apply credits when the credits reduce the payment amount below zero.
The following scenario illustrate the impact of this option.
Credit Amount Greater Than Invoice Amount
An invoice for 200 USD and a credit memofor 225 USD are due for payment.
The following table describes the payment processing that occurs based on the setting for the Apply credits up to zero amount payment option.
Assume that the "Apply Credits Up to Zero Amount" option is enabled.
Payment processing applies 200 USD of the credit memo to the invoice and creates a payment for 0 USD. The remaining credit is 25 USD.
References:https://fusionhelp.oracle.com/helpPortal/topic/TopicId_P_9F438E13CC89BA0CE040D30A68816F77