Choice "D" is correct. A direct letter of inquiry to the entity's legal counsel is required, and a client's refusal to permit such inquiry generally will result in a disclaimer of opinion. It is unlikely that a CPA would accept a new audit engagement under such circumstances.
Choice "b" is incorrect. Inability to review the predecessor auditor's working papers would not cause a CPA to decline a new audit engagement. The CPA would simply need to perform an appropriate level of work to substantiate the opening financial statement balances.
Choice "c" is incorrect. The CPA need not have an understanding of the prospective client's operations and industry before accepting a new audit engagement. Such an understanding may be obtained after acceptance, during the planning phase of the engagement.
Choice "a" is incorrect. Indications that management has not investigated employees in key positions before hiring them is a fraud risk factor that the auditor would need to consider in planning the audit, but it would not cause the CPA to decline the engagement.