Ralph & Sons, Inc., uses the straight-line method of depreciation for its long-lived assets. After a recent meeting with the independent accountants where industry depreciation practices were discussed, Ralph decided to switch to the double-declining balance method. In the year in which the switch occurs, Ralph should report this change as:（）
A. a change in accounting principle and report its effect on prior period results as a non-recurring item, net of tax.
B. an accounting error and directly adjust retained earnings.
C. a change in accounting principle and report its effect on prior earnings as part of operating earnings.
