Choice "D" is correct. A letter of audit inquiry to the client's lawyer is the auditor's primary means of obtaining corroboration of the information furnished by management concerning litigation, claims, and assessments.
Choice "a" is incorrect. While the attorney is requested to provide the auditor with the likelihood of an unfavorable outcome, the primary source of this information is management.
Choice "b" is incorrect. The attorney's opinion of historical experiences may provide some information to the auditor, but it is not the primary goal of audit inquiry letters.
Choice "c" is incorrect. While the attorney is asked to comment on management's description and evaluation of litigation, claims, and assessments that existed at the balance sheet date, the primary source of this information is management.