OO Corporation sold part of its voting shares of SUBCO. After the sale, total ownership was reduced from $22\%$ to $17\%.$ OO had exercised significant influence prior to the sale but is now unable to do so$.$ Assuming SUBCO shares have readily determinable fair values and that it did not elect the fair value option, OO must change to the

A$.$ Equity method retroactively.

B$.$ Equity method prospectively.

C$.$ Fair$-$value method prospectively.

D$.$ Fair$-$value method retroactively.