Choice "B" is correct. When the effect of a change in accounting principle is inseparable from the effect of a change in accounting estimate, the reporting treatment for the overall effect is as a change in estimate. Thus, the effect is reported prospectively as a component of income from continuing operations.
Choice "a" is incorrect. Restatement of all prior periods is the retroactive accounting treatment that is applied to the correction of an error and the retrospective accounting treatment given to changes in accounting principle. However, a change in accounting principle that is inseparable from the effect of a change in accounting estimate is now treated as a change in accounting estimate.
Choice "d" is incorrect. Correction of an error is given retroactive treatment as a prior period adjustment to retained earnings with restatement of prior periods. This is not the treatment appropriate for the effect of a change in accounting principle that is inseparable from the effect of a change in accounting estimate.
Choice "c" is incorrect. While footnote disclosure is always appropriate for an accounting change, such disclosure alone is never the appropriate accounting treatment.