Choice "A" is correct. If, during the current audit, auditors become aware of circumstances or events that affect the financial statements of a prior period, they should consider such matters when updating the report on the financial statements of the prior period. For example, if auditors have previously qualified their opinion or expressed an adverse opinion on financial statements of a prior period because of a departure from generally accepted accounting principles, and the prior period financial statements are restated in the current period to conform with generally accepted accounting principles, the auditor's updated report on the financial statements of the prior period should indicate that the statements have been restated and should express an unmodified opinion with respect to the restated financial statements.
Choice "c" is incorrect. The predecessor auditor generally would not change a previously issued opinion when reissuing the audit report.
Choice "d" is incorrect. A difference of opinions between periods would not result in the auditor changing the opinion on a previously issued audit report.
Choice "b" is incorrect. Restatement of financial statements following a change in reporting entity affects comparability of the financial statements, but would not result in a change in opinion from the audit report previously issued.