Over the Years,which One of the Following Has NOT Been

Over the years,which one of the following has NOT been an underlying reason for the growth in benefits?

A) The tax treatment of benefits programs is often more favourable for employees than the tax treatment of wages and salaries
B) The cost advantage that groups typically receive over individuals
C) The explosive growth in the number of small businesses within the United States and Canada
D) The growth of organized labour from the 1930s through the 1950s