After receiving responses to accounts receivable confirmations, the auditor determined that the evidence was not sufficient to form a conclusion regarding the accounts receivable balance. Which of the following actions should the auditor take next concerning the accounts receivable balance?

a. Issue a qualified audit opinion on the clients financial statements.

b. Withdraw from the engagement and issue a disclaimer of opinion.

c, Ask the internal auditor to evaluate the valuation of accounts receivable.

d. Request additional confirmations and perform alternative procedures.