We cannot say whether one allocation of resources is better than another allocation because ?

A. Productivity growth has been steady over the last 50 years
B. Productivity has been growing more slowly every decade since world War II
C. Productivity grew quickly in the 1950s and 1960s more slowly from the early 1970s through 1995 and then quickly again
D. Productivity grew slowly from the 1950s through the 1970s and then began to accelerate probably due to advances in computer technology