Final answer:
The auditors' report must include FASB or GASB-required supplementary information that provides additional context and details to the financial statements. Other client-prepared or auditor-submitted documents may also be reported on if they are relevant to the audited financial statements.
Step-by-step explanation:
The auditors' report must report on any supplementary information required by accounting standards which can include both FASB-required supplementary information and GASB-required supplementary information. The FASB (Financial Accounting Standards Board) and GASB (Governmental Accounting Standards Board) supplementary information includes additional context and details that may not be presented within the main body of financial statements but are nonetheless important for understanding a financial statement's completeness and accuracy.
As for the other options, auditors are typically concerned with financial statements that they have audited. Therefore, information in client-prepared documents and information accompanying financial statements in auditor-submitted documents may also need to be considered based on their relevancy to the audited financial statements and the auditing standards applicable to the engagement.