CPA Firm a Has Performed Most of the Audit of Consolidated

CPA Firm A has performed most of the audit of Consolidated Company's financial statements and qualifies as the group auditor.CPA Firm B did the remainder of the work.Firm A wishes to assume full responsibility for Firm B's work.Which of the following statements is correct?

A) Such assumption of responsibility violates the profession's standards.
B) In such circumstances,when appropriate requirements have been met,Firm A should issue a standard unmodified opinion on the financial statements.
C) In such circumstances,when appropriate requirements have been met,Firm A should issue an unmodified opinion on the financial statements but should make appropriate reference to Firm B in the audit report.
D) CPA firm A should normally qualify its audit report on the basis of the scope limitation involved when another CPA firm is involved.