C. The estimates used at the date of transition to IFRS should be consistent with those made at the same date under previous GAAP (after adjustments to reflect any difference in accounting policies), unless there is evidence that those estimates were in error.

When an entity adopts IFRS for the first time, it should prepare an opening balance sheet as at the transition date, reflecting the position of the entity as if IFRS had always been applied. According to IFRS 1, First-time Adoption of International Financial Reporting Standards, the entity is not required to restate periods presented before the date of transition to IFRS. However, any impairment losses recognized under previous GAAP should be reconsidered in light of the new accounting policies, and adjusted if necessary to ensure consistency with the estimates made under IFRS. If it is determined that the estimates used at the transition date were in error, they should be corrected. Reversals of impairment recognized on transition are dealt with according to the applicable IFRS guidance, which may not necessarily require restatements of prior periods. Therefore, option A is not entirely accurate, and option B is incorrect because an entity can reverse impairment recognized on transition if justified under IFRS. Option D is also incorrect because the opening balance sheet under IFRS should reflect all relevant accounting considerations, including impairment losses.