Final answer:
The management assertion discussing an entity's legal claim on assets and responsibility for liabilities under PCAOB standards is the rights and obligations assertion option (b).
Step-by-step explanation:
The assertion made by management in the context of PCAOB (Public Company Accounting Oversight Board) auditing standards that state an entity has a legal claim on all assets and revenues reported and has a legal responsibility for all liabilities and expenses is known as the rights and obligations assertion.
This assertion is part of the financial statement assertions that auditors use to assess whether financial statements are fairly presented. The rights and obligations assertion specifically deals with whether the entity has the rights to assets and is indeed obligated for the liabilities that have been reported in the financial statements.