Using the Chained-Dollar Method to Calculate Real GDP, Real GDP

Using the chained-dollar method to calculate real GDP, real GDP is calculated by

A) averaging the growth of output from one year to the next when the growth rates are calculated using this year's prices and using last year's prices.
B) valuing the current output at last year's real GDP prices.
C) valuing the current output at current year prices.
D) either A or C, depending which gives the larger value for real GDP.
E) averaging the value of current output valued using base year prices and current output valued using current year prices.