It Is Indisputable That the Degree of Inequality in the Distribution

It is indisputable that the degree of inequality in the distribution of wages has risen drastically in North America over the past 25 years or so. The most widely accepted explanation is that:

A) There are increased exploitation of labour by unscrupulous multi-national firms.
B) Cuts in social programs such as social assistance and employment insurance negatively affect low-wage workers.
C) The increased international competition and imports tended to positively affect low-wage workers.
D) The decline of institutions tends to raise the wages of lower-paid workers.
E) The returns to education and to unobserved skill have increased.