Choice "D" is correct. Comments concerning the unaudited interim financial information provide negative assurance as to whether any material modifications should be made to the unaudited interim financial information in order for it to be in conformity with GAAP.
Choice "c" is incorrect. Comfort letters are not required by the Securities Act of 1933, and copies are not filed with the SEC.
Choice "a" is incorrect. Comfort letters are addressed to the underwriter and are not included in the registration statement accompanying the prospectus.
Choice "b" is incorrect. The comfort letter does not update the opinion on previous financial statements. Often, underwriters will request that the accountants repeat in the comfort letter their report on the audited financial statements. Because of the special significance of the auditor's report, the auditors should not repeat their report.