A change from the cost method to the equity method of accounting for an investment in common stock resulting from an increase in the number of shares held by the investor requires:

a) Only footnote disclosure

b) That the cumulative amount of the change be shown as a line item on the income statement, net of tax

c) That the change be accounted for currently and prospectively.

d) Retroactive restatement as if the investor always had used the equity method.

What is the correct answer ?